Hehe. Mausers always remind me of the DL-44 (Han Solo's blaster). :P Makes you look like a Western version of Han Solo. :P
My only critique is that you need to weather it. You have done awesome work, but Bioshock is a very grimy game. You look like he's just walked out of a store after buying a new outfit. Have a good ol' Google of how to weather and distress leather, as your holster is just too shiny.
Weathering doesn't have to be really hardcore and over the top, but it's the finishing piece to a costume that really does make all the difference. He'll have marks on his vest from where the holster sits and rubs especially. I can see the weathering on the ascot and collar, which look great because they're both parts that would build up a lot of grime.
Also think of things such as the hem of the pants, even the inside ankle area where the shoes might scuff against each other under the hem, grubby hands going into pockets, grime on the knees if he's a kneeler.