Hey Denny, just had a thought on the 2D dungeon tiles that no other publisher has tried yet. Create 2D floor items that are intended to be printed on transparencies. There are probably many things that would fall into this category, but how about non-rectangular pits/holes; water regions; lava regions; blood stains; cracks or cravases; weapons/armor/treasure/coin piles/etc. Some objects that would have difficult edges to cut out could simply be cut out as a rectangle, because no ink/toner obscures the transparency outside of the object itself.

Other folks will probably have other clever ideas how to use transparencies. And for all I know, this idea stinks in actual practice...but there it is.

Almost forgot, stairs down. Stairs going up are great in 3D, but there really is no good solution (short of 2D), for stairs that head down.