There was a Russian company that I bought many themes from for my HTC. They were really nice. I just can’t remember the name anymore.
Probably 4pda.ru?
But yeah, WinMo was awesome back then. I still miss some of it’s features and customisability - no read-only system partition, no SafetyNet crap, physical buttons which could be remapped to anything (AE Button Plus), writing proper scripts using MortScript, modify whichever file you like without any issues. I still remember using this nice Windows XP theme on my HTC Tytn, with the slide-out QWERTY keyboard it really felt like I was using a mini PC.
It’s so sad that Android has become so closed now in spite of being technically opensource.