Afraid not. You have to beat the game at least once before you use any skin(s). There are 5 skins to be downloaded and 1 that everyone will unlock after they beat the game the first time on any difficulty.
Correct me if I'm wrong, but I was under the impression that the pre-order bonus codes for skins allowed you to play with that skin right away and everyone would have access to the skin after the game was finished once. I figured the bonus was to be able to play with the skin before you had to beat the game.
You're wrong. I looked that the stragegy guide while I was in Walmart yesterday (just wanted to see what exactly the Godly Possesions were) and it said that Dominus was DLC. There was only one skin that was shown to be unlocked in-game. Here is a thread that has a scan of the page.