Take off the trucks (wheels) and sand the board...not to much though. You just want to sand it down enough so the paint will stick.
(in this case it was a sticker that we wanted gone.)
Paint the entire bottom of the board with the background color of your choice.
Find a picture of Sally (or anything else you would like to put on it.)
and print it out.
Use a pencil to trace over the back part of the picture. Make sure that you get a lot of graphite on the lines.
place the picture where you want it...pencil drawn side down.
Then take the pencil and go over the picture. Make sure you do it kinda hard so that the lines you drew will transfer to the board.
Paint the picture (using the one u printed as a guide) If you have never done this before you always paint the background colors first and then the detail.
Add spider webs, bats or other detail to the rest of the board.
When paint is dry (I gave it a good 24 hrs) you need to seal it.
You can buy spray sealer at the craft store or wally-world.
Spray the whole thing and give it about 4 to 6 coats....let dry in between coats.
Let whole thing dry for 24 hrs then add the wheels back on and yay you now have a one of a kind skateboard ^^