I think that would be the idea, the floor and walls are bedrock, and obstacles stone.
I was thinking:
Floor/walls = Obsidian
Destructable obstacles = Brick
Items = Chests - things like water to defuse tnt or brick to create walls, maybe even obsidian.
Then there could be a bomberman texture pack so everything wouldn't look so fugly
OH How about soul sand to slow people down 8D