I've had some good luck with Vinyl Decals... I've never had one come off by board in years of use. Not as colorful as regular stickers, but they're less adhesivey and look sicker.
David Shu (Captain_542 on Wakeworld) has a Vinyl plotter and can custom-design vinyls for really reasonably, even for one-offs... plus he can design 'em in huge sizes (I think up to 2' x 2'). You should shoot him an e-mail:
dshu@purdue.edu.
Good luck with the stickering!