The 10G tropical tank that I adopted 6 weeks ago has a home made background. The young girl took some poster board and water color paints and painted a mostly dark blue and green background on the poster board and used it on the tank. It looks nice so I still use it.
If any of ya'll have kids or grand-kids, this would be a good thing for them to put up their art work and you could have them do a new one every few months if you want to change the scenery.
I've been thinking about doing some type of revolving "theme" background to go with the various holidays and then decorate the rest of the tank and stand. I'm going to try it first with a Christmas Tank (instead of a tree.. lol). Has anyone ever lined the outside frame of their tank with the small blinking Christmas lights? I don't know if that would bother the fish or not.