This one is fairly simple to do. I started with this sketch I drew of an angel (which incidentally; I drew a month before 9/11.)
This trick allows you to take any image of a brick/rock wall and put another image on it that in the end looks as if it were spray painted on.
Here's how it looked when I completed it:
Just a fun little trick with some cool possibilities.
The hardest part is getting the perspective just right. You're really taking a flat image and distorting it to match the direction of the wall.
By the way, I'm always on the lookout for fun pictures to use for various projects.
If you know of any, or you'd like me to try something in particular for you ~ Just let me know!