Playing around with some of the menus and option in NHL 08, I stumbled across a place where I could enter a code to unlock the jerseys. For a while I though this is something you probably have to pay for, but after a quick search, I found the code.
Not sure what the logic behind making you enter the code was; other than having you visit the NHL 08 website, which by the way has a horrible design and does not do a good job of promoting the game or the franchise at all.
So after you enter the code, the new jerseys become the default for the teams. You still have the option of choosing the older jerseys as well. One thing that I really like about the game is the attention to small detail. You can see the texture and stitching of on the jerseys. Pretty amazing. Too bad that the bigger details were completely overlooked - Weird puck physics at times, and the jerky motion of the goalie for example.
As for the real jerseys, I love the new Vancouver Canucks and Calgary Flames jerseys; and of course the Ottawa Senators (the white/away jersey). The new design worsened some of the jerseys in my opinion – Pittsburgh Penguins; the colours are just blah!!