When the PPCPE's came out they were creating custom ROMs. The only problem is all the threads I've seen about it were on Pocket PC Passion.
There was software us mere mortals could use to do it. The only thing I can remember about it is the term "Kitchen" I think it was the ROM customizing software. I'm pretty sure you needed a Full ROM upgrade file to start with though. Hmmm, you've got one of those renhui, maybe some google searching is in order. ;)