I don't think it's immense like APB, but pretty big. I wouln't put money on no one else looking a little like you.
BRINK will have more pieces of clothing than APB, I believe. But of course it doesn't have player-created texture-designs.
This link shows a fraction of whats avaliable
http://www.brinkthegame.com/features/customization/
According to Olivier Leonardi' quote those are 75% of all outfits.
We know that the Security will have "The Eel" as well.
And in the "A Choir Of Guns"-trailer we see a miner's helmet and a face-mask, which are both not part of any Resistance-outfit we know.
Also, I guess, SplashDamage will add new archetypes to the game in the future. And perhaps there will be bonus-items which are not part of any archetype-outfit in the future as well?