Good questions. As long as you follow the basic overview of what you’re suggesting you should be fine. You can sell the service of template customization to clients. So just be sure to be up front with people and let them know they aren’t buying the template from you, but rather buying the customization service. You should also know that when you buy a template on behalf of a client, the client is the holder of the single license.Using screen shots on your site should not be a problem at all!
Thanks for the reply MarkBrodhuber, good to head that I can use screenshots! I wiill keep in mind that my clients are license holders.