So then... Back in the day when Aquariums were new, all but 2 fish could only be bought with Cash and Booty Grab was the best way to make gold on the site Gaia released a wonderful and plentiful array of backgrounds for the feature so that people could customize one more thing for their fish... And some of them are actually quite nice and I think would look fantastic as avatar backgrounds!
There are, of course, some that might be rather hard, or look downright silly, if made, but there are also some that would look perfect!
Such as:
Court
Coast
Dojo
China
Paper Wall
Sunset
Road Hill
Coral Cave
Pastel Coral
Mountain
And, I'm sure, quite a few others.
So my suggestion is to please make at least some of these lovely backgrounds usable not only for the Aquariums, but also for our avatars. And maybe some more RIG headers as well *coughFinaLinecough*
I understand that the staff have quite a few things on their plate right now with the Avatar Builder and all but, the art is mostly already here in this case, all that would be needed is to select a specific part of the background and resize it for the avatars but, then again, this might actually be a lot more difficult than I'm imagining it...
Regardless, this is pretty much my suggestion for more backgrounds.