Square Box is doing some work right now in the area of expanding the availability of built-in fields for use in searches (Queries), but in the meantime there are other ways you can work to get the same result...
For example, if you search on the built-in metadata field called "Video" with the 'contains' operator and the frame size you're looking for:
"Video 'contains' 1920x1080"
CatDV will show any clip whose Video Format field includes that frame size, as a sample field value will be something like "Avid DNxHD Legacy (1920x1080 23.98fps)".
Another useful trick would be to use filtering to reduce a large set of search results to a specific "Frame Size", as that field is already currently available for filtering! In the navigation tree, select Filters>Automatic Filters>Technical Fields and you will then be able to see all of the frame size combinations in the found set.