If you use Find in Files instead of the standard search, you can search for a subfolder for the file types you specify.
However, it’s much easier to complete this task with the Ultrafind add-on (http://visualstudiogallery.msdn.microsoft.com/9fa9fdd7-1c06-45e3-a9f3-0381caab8f94), which you can use to exclude specific file templates.