There is a gallery of all (hopefully) skins on the wiki, here: http://musicbee.wikia.com/wiki/Skins
Larger sets of skins, like Dark Variations, I've been creating a single entry for and linking to a gallery showing all colors. (In fact, I've been linking all sets based on Dark Variations to the Dark Variations gallery, because I don't have the energy to make that many screencaps...)
Every skin name on the page can be used as an anchor link (it must be written exactly as shown on the page, replacing spaces with underscores). For instance, if you wanted to link to Mellow Blue:http://musicbee.wikia.com/wiki/Skins#Mellow_Blue
Feedback and suggestions/requests are welcome!
I'd like to encourage authors to add your skins to the wiki at the same time you add them here. There are some instructions (hopefully clear - let me know if not) at the bottom of the page: http://musicbee.wikia.com/wiki/Skins#Adding_a_skin_to_this_page
Don't be concerned about making mistakes. Almost any problem on a wiki can be fixed with just a few clicks.
You'll see that right now there are plenty of skins that still need to be added and a number that still need screenshots. Anyone feel free to jump in on these! Please and thank you.