So, we've got tiles for the bottom halves of Ground tiles. but not the top halves. How 'bout we add some o' them there tiles to this 'ere collection? *shot*
A potential issue I can see, though, is how all the other currently-existing Ground tiles could possibly morph with any new additions, and yet not morph any differently than they do now (wouldn't it break currently-existing levels to add these, maybe?).