Ohh map ideas? tons and tons, I love making maps and demigod? Infinite possibilities. (all of these assume that they can add somewhat advanced scripting to the maps(hopefully through the mapmaker

))
Underwater:
A shallow underwater map with magical Atlantien style barriers, perhaps random floods from collapsing fields, or random fields blocking passages
A deeper underwater map could have multi color lighting from fish or mythical deep sea creatures, or with volcanic vents and such.
Giant massive mystical stronghold:
Either on the ramparts and such or in a courtyard, capturable gates, catapults and treabucheas as well as burning oil and all that midevil goodness.
lightning/electricity:
Giant Vandagraph thingys shooting lightning across parts of the map hitting random areas, or perhaps an activatable parts of the map system based on charging capacitors and such
Moving:
Gears or moving map pieces so that the map could rearrange constantly
Flying or moving maps would look cool and could introduce things like changing spawns/effects/map accessibility.
Space:
Not only would it be awesome but floating map pieces and gravity manipulation (that'd be one powerful map editor!

)
Magical:
A map with diffrent parts of the map conveying diffrent bonuses: fire +dmg, speed, regen, invisibility?
Or with magical forcefields that could cut out or randomly spawn.
Weather/time cycles:
This would look awesome and there could even be game play ramifications, diffrent spawns during the day and night or rainy/snowy/sunny.
But again these all depend on how the demigod team formats its map files and makes it's map maker, I would love a powerful mapmaker (if your listening Devs!!!) the ability to change things like spawn ratios (what spawns and how many based on time/scripting) effect/model importing, the ability to script things like ai/neutrals as well as damage/healing/physics/damage bonuses/speed bonuses/other (de)buffs as well as having customizable controllable points/units with customizable effects (through scripting?) WOULD BE AWESOME!!