Cfg Loader can download themes from the official repository on its own. There is an option "Update Themes" in the Global Option menu (press 1 two times). After updating the theme browser pops up. There you can watch a full screen preview and download the themes. The used theme can be changed in the global options or the config. Speaking of config, there is an option for showing adult themes that is turned off by default, but they are not that great in my opinion. Only turned it on out of curiosity and left it on to have a laugh sometimes.
There are probably more themes on the Internet, but I never searched for them. Simply ask Google if you don't find a good theme in the built-in theme browser.