A small reward for being wanted and surviving would be a reduced experience penalty if you're killed by a charmed mob (i.e. necro pets, conjie mobs, called guards, etc). Sliding scale based on how long you survive as a criminal up to 0% experience loss.

If that's a bust, how about a couple of shops that will only sell to you if you're wanted (or will give you access to more items if you're wanted) since most shops won't sell to you if you're wanted.

Not sure I'm a fan of the sliding scale for experience loss.

The shopkeeper thing makes sense, more of the black market types that thieves fence to & such. Always willing to make a buck.