bp.org probably wouldn’t host such a thing, but I can imagine some BuddyPress fan site implementing such a feature!
Until then, you can host your CSS code and sample HTML on Jsbin.com for easy previewing.
I’ll check it out. As I’m sure you know good themes are a bit rare for BP. I was just thinking “Skins” may be a good way to promote BP usage. I would love to setup a site if I had the time. There are are growing number of good BP topic sites so hopefully one of them can give it a try. I think it would drive a lot of traffic.
@fiq feel free to create a child theme of the BP Default theme or a BP-aware WP theme and submit it to the WP Theme Repository https://wordpress.org/extend/themes/upload/ Let me know when you do and I’ll review your theme
For your reference ->https://codex.wordpress.org/Theme_Development_Checklist
Perhaps there should be a simple skeleton child theme with an admin option for loading and switching between different style sheets. That way submitting designers only have to do the css and not the child theme skeleton. Have it somehow assign a unique id to each style sheet. Because there are no template changes you could use any of the style sheets and switch between at any time. You could have a different look everyday. Because there would be no php changes to the default BP theme it would be easy to support.