I’ve lately discovered how much fun it is to doodle some scribbly designs and plop them in a blank Photoshop canvas, shuffle the pieces around, and make a little pattern. I did most of them in grayscale so you can just use Screen/Multiply on them. Here’s some tiled patterns I made for free download.
If you feel inclined to let me know you’re using these patterns and credit me with a link, I’d welcome it greatly. Here is the pattern set for Photoshop.