Prices for Signatures:
You pay with Reputation, which you get by posting.. or because someone donates to you, whatever.
1 Picture - 1 Background; 50Rep
2 Picture - 1 Background; 100Rep
3 Picture - 1 Background ;120Rep
Prices for Avatars:
1 Picture - 20Rep
2 Picture - 40Rep
3 Picture - 60Rep