I've had more luck in emailing or snail mailing the management or record companies of different artists. I've gotten a few autographed pictures like that, and some giveaways to give to the kids that I teach. Jack Johnson's wife sent me like 75 stickers to hand out to my students like a year and a half ago. It was really cool.
I can understand about not wanting to seem like a stalker outside of a venue. Once I was at an Oriole game a few years ago with a buddy, against the Angels. I was walking out of the stadium late (I had been waiting for an acquaintence to get off of work) and some guys came out of the Eutaw St. gate walking toward Howard St. I was about half a block behind them, and they turned left on Howard St., as did I because I was parked near the Balto. Arena. About another half a block up, this asshole turns around and yells at me for being a fucking stalker (verbatim). It ended up being Tim Salmon from the Angels (who was doing the talking) and Darrin Erstad was with him, and some other scrub. I was so damn pissed, I yelled "why in the hell would I be stalking you? learn where to walk asshole, you could have walked down Conway St. to get to your hotel. I'm just going to my car another block up." I was by myself at the time and was worried like hell something was going to happen. He just turned around and flipped me off and was mumbling to the others. The Angels can go to hell after that experience.