Depends whether you want custom CTF themes that work on custom firmware or PTF themes that would work anyway. CTF themes are a bit hard to find, since most of those themes were made for PSP 1000s back in the day of 5.03 GEN cfw. I'm sure some exist though. PTF themes are an entirely different story, since they would work on any psp as all it does is change the background and icons. Google is usually the best place to find either.