Since then I've stopped by several times to see what's new. I never did catch Joe (I still haven't met him... he's one of Tucson's busiest muralists), but I did catch some snaps of the mural taking shape. January 20th, LL Cool J was in his place on the right panel:
The right panel seemed like it might be almost finished...
Back from my trip to South America, I rode over the snake bridge to see the mural. It looked finished:
You can see that it's filled with (mostly) famous people, (mostly) musicians, surrounding Mount (Mick) Jagger. Here are close-ups: