No, you don't get weird plug-ins to dress up the characters as playboy bunnies or anything like that, these are a bit more gaming-focused items. First up is a Hard EX Mode, which makes the enemies more difficult AND you lose your Edelweiss tank-- a much tougher battle. You also get two missions in the pack: one in which you play as Edy and try to regather the six members of your team who've been separated, and one where you play as a meek engineer who must help defeat his enemy. The catch? The engineer fights on the Selvarian side-- against your characters.
Interesting stuff! When I (finally) buy Valkyria I'll probably consider snatching this up, mostly for the Hard EX mode-- how about you?