I'd go with the basics of magic aura, prestidigitation, and other mundane disguises. Odds are, if you're going to be found out your DM plans to use it as a plot hook anyways (kill the mage who's blackmailing you before he tells the paladins about you).

Another idea would be to make it well known that you killed a VERY evil creature and took a trophy magic item from him. Then even if someone pierces all your illusions, you can claim they're detecting the evil artifact. Won't work for too long, but if you claim that, say, they have no experience with evil artifacts or that their experience is with artifacts exposed to a lesser evil (combined with a damn good bluff score) you might pull it off.