Git'yer maps HERE

Having a rough time getting a solid design for a map that isn't affected by theme, so rather than focusing on the layout of the map I think it would be better to present new and altered map elements, at least until we've settled on a theme.

Falling: Dropping from high up could cause a brief stun (no damage) as your character rolls out of or absorbs impact. Ninja would be immune.

Sand: Slows acceleration, instant stops and turns. Falling onto it from high up doesn't cause a stun. Possibility of hiding Gnomes and Items under it.

Quicksand: Slows all movement, weakens jumps. Slowly covers the body, possibly disabling commands as you get deeper: no jumping once your legs are covered, no attacking once your arms are covered, rapid (somewhere between water and lava) damage when head covered.

Shiftsand: Operates like sand but with momentum. Basically conveyor belts but with more a more fluid pull.

Water: Some classes able to swim/hold floating items to reduce speed reduction and avoid drowning damage, Ninja able to water walk while Cloaked. Possibility of flowing water.

Hiding: Areas where you can keep your name hidden and be off the enemy map if you keep still.

Lava: Some manner of lavaproofing yourself for a short time? Likely created by the Blacksmith.

Creep: General term for actively hostile terrain. Potential elements: sparks/arcs of electricity, swarms of rats, aggressive vines, spreading thorns, exploding objects (grow slowly then explode when someone is near), cursed ground (lowers stats).

Haven: General term for actively helpful terrain. Potential elements: blessed ground (boost stats), healing zone, warded ground (neutral when empty, prevents opposite team from entering when someone is inside), duelling area (will only allow one person from each team in at a time, may give reward to winner of duel.)

Nearly have a habitat for each class. Once I have that sorted, I'll start with the layout using the simplified method Aeolus proposed to get my head around hazards and build zones and such. Thinking about maps more has lead me to realize that some objects should be set to one area because they're too complex to do otherwise. Bridges for example... if they can be built anywhere, how are they transported to a place that makes sense? You'd need a lot of escorts to move something that heavy. Some objects make more sense linked to useful locations.
Another thought is outpost flavouring. With so many different environments, outposts should look a little different in each. A shield instead of a door in the Alien's map, a thatched roof on the Shaman's, a fusebox in the Robot's... things like that. It doesn't need to apply to things Robots build, since those are brand new, but objects that have been there a while should fit the scene.