Are you trying to use the *exact* size of 1000x1000 as your standard? So for example, 1000x999 would still be picked up by your smartlist as "invalid" ?
I take an alternate approach of looking for images that are less than a certain dimension. For example, I would be looking for *either* image height or image width being less than 1000. Actually, I usually fudge about 20 pixels, so I would look for less than 980 on each side.
I've actually built a custom view to do this for me. I can switch on and off the criteria of less than my specific size. I also look for images with no cover art. I'm attaching a screen shot for illustration.
Because I might have art with unusual dimensions, I've also got panes to let me isolate by widths or heights. This helps with unusual stuff like a very tall image (like for a boxed set), where it's plenty tall, but it has a small width. Yet this is acceptable.
Which brings me to my final piece of the puzzle: I have a custom field (Image Approved), that I use to mark cover art that falls outside of my specified size, yet I consider it to be good enough and I don't want to see it in my list of "invalid art". One of the panes in this view turns on and off that feature.
Brian.