I think it would be interesting if you could shift click the block, and it brings up an interface, with the flat block side on it. Then you can click the pixels, and they would darken, like you were chipping away at the stone.
This would make them customizable, if you are willing to put a little extra work into it.
If you see up there, on your textures, it has a lighter edge right next to the grooves, in both the bricks and the grids, and it might be nice if it did that automatically when the "groove" got deep enough. You could cancel or undo as well.
So if you don't like creepers or Withers, but you like Endermen or Skeletons, you could carve their face into the stone instead! Or make arrows to point the way, or cool words in the blocks, or a code made from runes for you and your friends, or a puzzle map that looks amaaaaazing!
Then, you can craft that block with the chisel and more blocks to copy the design, which would also take durability on your chisel.
A bit more detailed than most of the rest of minecraft, but it would have so many uses.
I love your idea! Gave me inspiration, which are the best ideas Support!!!