There are lots of options out there for backdrops, but if you want to pair them with a banner stand, as seen here for our GIF photo booth in Austin, TX, then its preferred that you use a backdrop fabric with pole pockets sewn in. This makes for a nice clean presentation as well.
Some very nice backdrops can be found all over the web, but here are some personal favorites.
Drop It Modern | for high end luxurious backdrops.
ShutterQube | for fun petals and textured backgrounds
PhotoPie | for custom printed fabric backdrops. Very High Quality.
Bubblegum Backdrops | has several unique items and offers pole pockets.
Ink & Elm | provides nice quality in either solids or designs, with pole pocket options.