There are 12 maps to play on. Make sure you do them all. That was my problem at first, I was only looking at the pics and not the name of the level.
Looking to boost:
(Please send a message with friend request or I will delete it
Bioshock 2 (Rapture Metro DLC)
Blacksite Area 51 (anything but CTF)
100,000 GS 12/31/09
200,000 GS 05/29/12