Industrial designer Andrey redesignd U.S. bills, starting with the material: Polymer, imagines greenbacks as modern plastic banknotes, similar to the more daring bills in Australian and UK currency, with UV-readable serials that are repeated in QR codes with PGP-signed hashes.
They look more like high-end collectibles than fiat, and they miss an important usability aspect in that they're all the same size, rather than following the sensible custom of printing larger-denomination bills on larger sheets.