Shadow for Eroded Tiles

I was looking for dungeon tiles to print on chipboard for my next Pathfinder game, but I disliked most I could find. So I made my own shadow to lay over stone textures. For best effect with Gimp use the shadow with "grain merge".
Be my guest to use this shadow to your hearts content, but please give me a notice if you post the outcome. I would like to see them!
Some of the tiles I made with this:
Green Dungeon Tiles
Grey-Red Dungeon Tiles
Marbel Dungeon Tiles (checkered)