Yes, I, too, have noticed the "suspicious" 
backgrounds, but as long as she does not claim 
they are matching and specifically claims that 
she "doesn't know", it becomes a matter of "buyer 
beware", not a criminal matter. It is hard for me 
to avoid Marcia's auctions because I search ebay 
based on the words "anime cel". I have not bid on 
any of them, but considering they don't go for 
very much, they have probably made some people 
with limited budgets who aren't too picky, quite 
happy to acquire them. No harm in that.

However, unlike some, I'm glad you posted because 
it may be of informative help to some others.