Lately I've been working on a Rock Raiders map where everything but the materials and building models were made from scratch. Ben24x7 has already volunteered to make an Ice themed map. If someone wants to make a lava themed map and at least knows somewhat what they're doing, I'll send the resources over.
And now for screenshots.
Walls, these are destructible and different types have different strength, I've also added in slopes and made the front row of walls not square:
Water, can be driven on by the airboat and you can't walk into it. I've lit up the area so you can see better.
Lava, this burns you but can be driven on, again you cannot walk into it.
Hammer view, this is what it looks like in the map making program. I've covered up areas of the cave with the ceiling as to not reveal too much. That being said the map is still a WIP and is subject to change and will definitely get expanding.