Go to the street on which the bully/bullies live, take a camera with you. Before he heads out for school, make sure you hide. Then when he steps out of his front door, take a picture of him. Stay off of school that day, and later on, before he comes home, put a printed version of the photo through his letterbox, or better yet, nail it to his door.
Even better, fill a squirty bottle full of something flamable, go to his house while he's out, make sure it's empty, if his parents work, then good. Take the squirty bottle and either squirt it through his letterbox, or through the keyhole. Either leave a note on his doorstep weighed down by a lighter or a match (make sure it doesn't look like your hand writing) or put a note and a lighter/match through his letterbox. The note should say: "Next time, I'll light it."