At the end of the campaign you get given skins of the US armies you played with.
No OKW ones.
We hope Relic will make all WFA and AA skins purchasable at the steam shop. It has been discussed at another thread some time ago.
(Source)
As you probably know Cynthia_RE wrote there:
[...] I'm not saying you guys can't look at this stuff and speculate, but you need to know that this is not some sort of holy grail when it comes to pre-anticipating things.
This being said, we know that there are items that people want to purchase, that they currently can't. It's something we're looking into
This beeing said, Relic knows. Will this ever happen? Nobody knows.
But I promise I will be very very excited, so excited, if I can get new skins for U.S.-Forces and OKW. It's something I´m looking into.