I have three DNN skins but they are similar. The difference is the style of ContentPane. Is there any way to create some "master" skin with header and footer and three subskins with different styles of Content pane? Because it's a bad idea to create skins which have 99% same markup, the only difference is content pane style.
You could abstract the Header/Footer sections out in to their own ASCX files (referencing those from the main SKIN files), and then just have the Pane portion of the file be the differing part.
The other option would be to have One skin, with three different Panes, and instruct your users which PANE they should use in which scenario.