If you turn around you see it's part of a larger artwork, The Wall las Memorias, the first publicly funded AIDS monument in the nation.
Roberta (Latino Heritage) mentioned this yesterday in the comments. You can see the horseshoe peeking out from behind it. It's actually not a horseshoe, but a design based on the AIDS awareness ribbon.
Karin posted another part, where the artists included pictures of themselves painting the mural. The whole thing is witty that way. I love how in this panel the artists incorporated the night deposit box as our hero's footrest.