I like good ol' Nirvana covers. The basslines are totally do-able, get your hands moving around the fretboards, and are kind of cute and retro. They're lots of fun. And RHCP, which, depending on the song are not as stupidly difficult as you might think.
Learning actual scales and stuff is good too (um, probably essential actually, but you know the theory, so probably less of a necessity for you), but throwing in some tabbed songs (or even playing from ear if you can) is good practice in getting your hands moving, building up some big-ass callouses, and keeping your interest. And that's most important. Having fun playing stuff you like. Anyone with an ounce of musical knowledge can be an adequate bassist, and given that you're a proper muso, yeah, you'll have no probs.
