Somebody from xda-developers claimed that he ported Samsung's TouchWiz to Android 2.2 for the Nexus One. Even if some users said that this is something great, what I think is that Android's 2.2 default interface looks 10 times better than Samsung's TouchWiz, but this doesn't matter. What is important is that that person worked to do this, so that's why we have to appreciate his work.
He said that it works on the FRF83, so if you're FRF91, I can't guarantee you that it will work. I wasn't able to install it, as the user said that it needs to be installed with adb. It fails to install normally ("There is a problem parsing the package"), and, from what I know, adb means Android Debug Bridge. If I'm right, there's a quite complicated process which needs to be done, but you can try (use Google, it will help you) if you want to.
Original Source and download on xda-developers.