Well, I started making my own book covers (but didn't take any pictures) and my friend wanted one. He's a big A7X fan and loves Coke so I knew exactly what I wanted to do.
It's easy, just make stencils. :D
First, make your book cover. I'm terrible at this step! You can find some instructions on how to do this online if you don't already know how.
Ok, now that you've got that bad boy on there it's time to choose what you want to put on your book cover.
When I did this one I decided I wanted to do A7X's bat thingie.
Pick your picture and get it into stencil format.
Alright! Here comes the tricky part. Take your image and cut it out using your cutting knife. Make sure you're on a hard surface you don't mind scratching up. Depending on the picture you chose, this may take a little while.
Now we have a nice stencil! Good deal.
Tape it down onto the book cover.
You can also use spray adhesive. I use Easy-Tack because you can move it and it won't rip up the book cover. Whatever you choose is fine. :D
Pick your paint and paint over your stencil. When you're done you can peel off the stencil and admire your work or leave it on and spray over it with a sealant to keep it shiny and keep it from flaking off.