One thing you have to remember as the developer is you will alway's be the one implementing the resources the designers give to you. For instance with the topic of themes. A designer is not going to be placing ASP.NET controls on a page (well not usually). When they design a form it will usually show standard html inputs just as place holders. And you the developer implement your .NET solution. Same thing with master pages and themes.. Let the designers use what they want, You get what they give you and fit it in to the master page. On average that will maybe take you 5 to 10 minutes to get a designers HTML doc transformed into an appropiate Masterpage file. From there you would add your content areas and so forth. You as a developer really should never have to concern yourself with what the designer is giving you as long as they are giving it to you in a compliant format that you can then take and implement your solutions as you are now.