Oh, I think you are referring to not leaving a gap due to selecting within the black lines...easy fix, once you select all the blocks use edit>grow>1 pixel. Do the same for the opposite blocks and you have everything covered. (btw, I'm using Gimp lingo but it should be close to what you have in PS).

If you mean the actual texture I used I don't have one. I just loaded it with stones and used the mosaic filter on it then fiddled with it a little.

Hopefully, I answered your question, if not just ask again. I'm going out of town this weekend so if you are really stumped I'm sure one of the other folks around here can explain my gibberish