For prints, you might try this shop that's above the Prado heading towards the Retiro Park. I don't know the name of it, but it's right next to the Casón de Buen Retiro, on Calle Felipe IV. For more modern stuff, you can try Fan (Fann?) which is on Velazquéz. Starting at the beginning of the street it's on your right before you get to Calle Goya. Speaking of Velázquez, if you walk a little futher (past Goya) and go a block or two, you'll find on the lefthand side a store with decent souvenirs. I think it's called Museum-Musei. Anyway, the gifts are a step up from the usual stuff and the price range is pretty wide.
There you have a few ideas...sorry about the vague directions.
As for shoes in the Rastro, I'll let someone else field that one, but I'd be wary if I were you. Clothes at the Rastro in general are of pretty questionable quality...and often not the bargains they used to be. At least, that's the impression I got when I last went.