At most fish stores you'll find the usual natural looking backgrounds for your fish tank. If you want something more unique and different you could use a little tape and adhere nearly anthing to the backside of your fish tank...posters, pictures, drawings, wrapping paper or even these designs I created in MS_Paint and printed out (it does help if it's waterproof if you're concerned about possible water damage).
Tired of looking at tacky fish food containers? I like to use a small spice rack to create a colorful display peice by my fish tanks but you could also use any other type of storage containers or jars.
Have any creative tips of your own that you'd like to share? Drop a comment or two, I'd love to see your creativity!