Disclaimer, I am a retard when it comes to names.  So for the sake of this feedback post I dub them the following so that we are clear.     Mostly its nit-picking, but somebody has to do it.  I'm not sure how much effort is going to be put into improving the maps before release (its all about making the game function on all levels and balance at this point right?) but just in case:

"Small map"   =   map with frozen deamon thing in center
"fire map"   =uh, the map with lava and such
"skeleton map"   =  Map being supported on the blades of skeletons, biggest available
"maya map"  = big map that takes place on what looks like a mayan temple
"aquaduct map"  = the cataract or whatever, mostly square map with water flows
"Water map"  = leviathen or something like that.  The less-greek and more watery of the two maps with flowing water.

The small map has a cool concept, but it is visually distracting because it has a strange boarder to the entire map.  It has like a white dotten line that follows the edges of all the cliffs (not including background).   I'm not sure if its my graphics card or what (Geforce 280 GTX), but its annoying. 
- another problem is that when playing on this map with fortresses, upgrading to include trebuchets allows the fortresses to directly attach each other, This is a pretty big piece of cheese.   First to get trebuchets basically owns half the enemies fortesses (and likely players are following the creeps, ignoring the side fortresses)     I think an easy fix is just to not let fortresses directly attack each other.  Unless, of course, you want that to be a strategy available (be on the defence until you get the def-upgrade and you can attack each other)

The fire map has a bunch of problems mechanically it seems, but visually is very nice indeed (I would say sexy, but... well, I coment on that)
- 1st off, there is a pathing problem that when you're standing in your base and you declare you want to go to the center artifact shop + flag, the characters rush to the back edge of the base and stand there looking stupid.
- 2ndly, It is WAY too easy to snipe the enemy portal.  you can teleport to the portal from the center part, and there is an area where you can stand and capture the flag without being in harm's way of the archer towers.  
- if you do steal the enemy flag (which should be harder than it is), I think you should be able to attack the stumps on either end of the protal prior to them becoming towers.    You might be able to solve that  problem by making them never not-towers, so that way the portal is protected at least a little.
- This map suffers from the center fortresses can attack each other like the small map did.  Its the one on the center of the map.  They are usually the last fortresses to be standing when I have played it as well, which brings me to the next point.

-   The center flag should be more important if creeps are never going to reach it.   Like I really don't care about the shop, and 1 buff really isn't worth letting somebody beat on my towers.   But if there was something seriously battle shifting there, then maybe it would be more often contested.
-  did anybody other than me notice the fire map looks like genitals?  I mean I spun that map around and pointed it out to my roommate, to which he could only reply "hot" * is joking *

Maya map:  visually this map is pretty sexy.   However, the background leaves something to be desired.   At least on mine, the horizon has a bunch of floating particles or something.  It looks like parts of polygons that are clipping into draw distance, but the model that connects to the terrain is missing.  
- The fog is a nice touch, but for some reason it seems lower quality than the regular fog of war as defined by my video settings (which are on high)   also, they rub against polygons which make it clear where one bit-o-forest ends and another begins.  Again, its rather distracting.   
- on one side of the building, there is a rock sticking out of the cliff face, the forest that sticks up in front of it has a very not-smooth edge, and it contrasts heavily against the rock.
- the backdrop on this map I guess could just use a good touching up before launch I think, it seems lower quality than most of the other map backgrounds.  (it would be awesome if the sun rose during the battle and had the shadows cast the way it looks in the trailer.  I'd forgive it for being simple)
- I know that just getting collision to get knocked back minions to land on the terrain correctly is probebly a challange you've already decided how to handle, but I wanted to mention it would look better if the minions would bounce against the cross-hatches covering the holes in the map.  Right now minions just fly through it like there is nothing there, and thats great if they are mostly in one of the holes.  But they pass through the bars too, which makes them look like a flat poly and cheaply made.   I am sure collision on all those little holes might be stress on some systems (maybe there should be options about that, so that the systems that can handle the collision calculations can.)   Deal with it how you will, again I'm just being nit picky.

aquaduct map:  I intended to say this last beta, but I forgot.   ON lower settings it seems that the waterfalls turn off almost entirely.  Like there is splash particle spawning near the top of each fall, but the actual current between the top and bottom appears to be missing and it looks ugly.  (Geforce 7800 GT OC was delivering the low settings)

Water map:   I really don't have anything to say, other than the water maps could maybe get splashes when units fall in?   If not' its probebly not a big deal

The skeleton map:   This one...  this one is tricky for me to give feedback on.    Like, the map is pretty awesome mechanically.  It seems balanced, one side is by default in a lock, the other has the portal that will shift the tide based on who controls it.  So I really like that part.    But everytime I look at it, I feel let down.   With all the other maps having something going on in the background (water flowing, lava falling, rolling fog) this one has nothing.   Its like I want to see green mist rolling out of the skeleton's mouths or something.  

Its not even the lack of animation either, since the small map doesn't really have anything like that, but the small map has a story that I can see.  I know that the creature was prisoned there long ago, and it makes me wonder what for or how.   In that map, its simpleness is its bliss, leaving me constantly rotating my camura to try to get a better look at the beast.

To get back to my point on the skeletons.  I just don't take anything from it.   Like, I do not understand its purpose or why we are fight on it.   All the maps I can imagine represent a place of importance, except this one.   If I were to pick which maps didn't belong with the others, I'd choose the prison and the skeleton maps.  The rest all seem like temples or similar buildings that were built (or just has always existed, like olympus did for the greek pantheon) for the gods.     And then I'd pick the prison to be the one that goes back with the temples, because it is the one with a story behind it.   Obviously the being imprisoned has enough significance that the place has become something of a divine area.  Perhaps the battling is something of a torture for the creature, forced to exist unable to move staring up at war raging just beyond its blood thirsty reach.  Maybe the fighting is giving power to the deamon so that one day it can be released.  There is unspoken story with the beast, showing the last expression it wore before it became frozen in the mountain.  I understand what makes it significant, its a prison.  Everything else I can make up for myself and the map is still just that, a prison upon which we are fighting.    

The brothers though, I can't figure out what story there is.  I know they are brothers, and I can see they are supporting the battle field.   But that doesn't give me enough grounding to really start any kind of idea on why its important.  Surely it isn't the exact same story of being imprisoned that the small map carries.  That would be boring, with so few maps to already be repeating the same idea.  But what else is there? 

perhaps once we have the final product, I'll understand the skeleton map.   This is just feedback on the setting and feel of the game, so take it with a grain of salt.   Perhaps its too late in production to make any significant changes to the map, or maybe it isn't worth doing it since the mechanics are better solidifying.  I just figured its feedback better given during the beta while there is still chance to change the maps, before they are launched.

Quick summary:
Skeleton map  >   could use some spicing up with some kind of flavor
maya map >  background could use a make-over
Water and Aquaduct maps > maybe splash animation on falling creatures?
prison > get rid of annying boarders,  I personally think its broken for fortresses to attack each other
fire map:   Center space isn't used, should be improved.   It shouldn't be as easy to steall other people's portals