It seems to me that people care enough about it to pay for it.(just search "my background") and personally, given the right price, I would.
I'm asking this because I want to know when do people pay for complementary features. things that are not necessarily meaningless but doesn't affect the functionality.
so, would you pay for it? if yes, do you think it would make a sustainable business model?
just to clarify:
I wasn't talking about making custom backgrounds I was talking about twitter itself. in a freemium business model, you offer the basic Web service for free, while charging for special/complentary features. hypothetically speaking, what if twitter charged for the ability to change your profile background. Hope that made sense