The target is to show nodes with images on top and nodes without image after. It sounds like a straight forward requirement that Views could do it. Unfortunately, module filefield doesn't provide such filter to View.
Bug: The profile_role module will check the user's role before allowing them accessing to the profile fields. When the profile fields need to be shown on Registration Form, the module sets up a exception that checks if this form is user registration form then don't check user's role.
This article may help you if you plan to install CentOS 6 and memcache on a virtual box in Windows. While going through the installation I have made some notes which may help other people doing the same.
Views is an amazing module not only because of its UI for query generating but also as it provides comprehensive hooks. Sometimes these hooks confuse beginners with their sequence. Here is the processing sequence of these hooks for your convenience.