Crocotile3D is a super simple tool to turn 2D Tilesets into 3D scenes. The app is limited to dragging 2D planes into a 3D space and arranging them into 3D objects and scenes. But that limit makes it work really well and really really fun to use.
A lospec charac like this legionnaire just took me minutes to complete. So if that kind of stuff is your thing, give the program a spin and consider purchasing a key to access saving and export features.
Check it out here: http://www.crocotile3d.com/