This user has the same IP address as the loser who
was "selling" Cowboy Bebop cels that he didn't own
a couple of months ago.  Even if you WERE inclined
to sell him a copy of your background (which I
agree might not be in your best interests as a
collector anyway), I'd be damn sure to ask for
proof of owning those cels before you gave him
anything.  And even on the remote chance that he
does have the cels, ask him whether he plans to
keep them or just dump them for "highest offer" to
the hungry collectors who missed out on the
original auctions.  After all, even copy
backgrounds tend to increase the amount of money
you can milk out of the cel community.

This is, of course, assuming that the original
poster is the same as the previous scammer... but
it doesn't hurt to be sure anyway, right?