If you happen to dig vintage graphics, COL.LECCIONISME COIXET is a store you can't miss. The amount of graphic memorabilia they stock in their rather small space is quite impressive. Yesteryear inspiration galore in the shape of posters, postcards and all kinds of advertising artifacts at prices you can afford.
Check them out at Banys Nous 19.
No, they don't have a website. Ebay? No way!