I like the second idea. Perhaps, when submitting (or updating a skin), the submitter could include a link to the forum. If the submitter chooses not to, the link will link to the subcategory of the skins forum, like you had suggested.Comments on a forum thread would be a good idea (I don't want to add a whole comment system to the skins page). Should each skin link to it's comment thread? or should I just create a subcategory of the skins forum category and let the users find/create the appropriate skin thread? (The second solution would be way easier, it's actualy what they use for comments on xkcd.org)
About the version number ... yeah, we could display it. Or maybe just increment a counter each time a skin gets updated.
I'm not too sure a version number needs to be displayed. It would be nice, but the current download page does a decent job telling when a skin was last updated...