Oh, posters! YMMV obviously, but I'm absurdly fond of the ALA "Read" posters in all their dorky glory. If you're into Edward Gorey at all, The Gashlycrumb Tinies make for amusing wall art. If your walls can stand it, you might consider something more decorative like this Charley Harper flock of birds wall decor or the multitude of wall stickers available on Amazon (there are generic ones and lots of fandom-y ones, depending on your comfort level in a public-ish space)?

Thank you for the Murderbot link. I keep meaning to mention that one to Mr G. Though given your enthusiastic recommendation, we might share it. :)