Hmm... that's weird.
Well, unless your PS3 is having some problem to recognize backgrounds, it could be something about the size or the format of the images you're using... but in that case, Theme Builder would have warned you, while building the theme.
Did you have the same problem with your other themes, or it's the first time?
So far just the Mortal Kombat theme i uploaded here, and another Mortal Kombat one i was working on. I'm starting to think it has to do with a certain wall paper. I'm going to maybe try loading and reloading the theme until i can see which paper it isn't showing. My Brink theme seems to be ok as far as I can tell and it has multiples as well.
Uh, I almost forgot...
To use an image as avatar, you just need to go to "gravatar.com" and follow the instructions. But before doing that, I think you also need to register here, because I see you're still a "guest". That's because your gravatar will be associated to your e-mail address, but if you don't register/log in, it will never be displayed...
well the loading and reloading works...and doesn't at the same time.
now this might just be bad random loading or it might have to do with how the system works...but...
if you sit at the theme menu and just keep hitting apply, it only cycles between 4 of the six backgrounds (tested with my Brink theme)
i did however luck out and one of those four (in the mk theme) was the "bad" one. had it been number 5 or 6, not sure i could have found it with this method.
Well, as I said, your PS3 might have some problem, but... the fact you say that applying repeatedly the theme, the PS3 always displays the same 4 backgrounds of the 6 available, makes me think that it's just a problem of the 2 remaining backgrounds (especially considering it already happened with another theme)...
I think you should check them again, because maybe their format has something wrong and the PS3 doesn't recognize them: be sure the jpeg format IS the standard one.