Silkscreen ink is cheap! Then all you need is a foam roller and something with a cool texture. If you want to get fancy, you can cut a mask out of cardboard, matboard, ABS plastic, or (other cheap material I love to use) tile-board.

Pirate street art

Pretty much anything that has a cool texture is a candidate:

fish prints

I do not support hurting octopus, though. There are some amazing inanimate objects out there with lots of texture.

hipsta street cred!

None of  these are mine. I did a lot of silk screens when I was in high school, most notably one that read “ALIEN” and “In space nobody can hear you scream” on the back. The belly and back were both printed with a giant red blood-colored blob, which I then shredded with a knife. My sense of humor hasn’t gotten much more sophisticated since 8th grade, really.