I do something similar as you do OP. One thing I greatly suggest is you testing the skins in a test / side parent portal etc. 99% of all skins will work but there are tons of skin / container issues that can come about. If the user has a pure CSS skin but uses a container that uses solpartmenu IE a default one / other custom container. Its possible about 75% of the time the container menu will not position correctly in the skin. Its very hit and miss and no way to tell upfront. In general most skins / skin packages come with a working / matching container included, but still doesn't mean your client won't try and use DNN-Blue container with their custom skin. I actually had to start a listing of skins and incapatable containers I offer on my site. For licenses typically they are good for all portals on 1 DNN installation. Mainly cause its difficult to prohibit their use on parent portals etc. I don't recommend allowing Admins to upload skins, I tried it for a while and had half my customers try to build their own skins which created lots of overhead for my database which caused issues with other clients. I offer them custom skinning options, and still allow them to build their own but I go threw it and clean up the skin and test it before uploading it.