This question is really about creating a process for reviewing your album art. When I was doing this, with a collection about 1/5 the size of yours, I created my own View for this. It is a Panes View with custom panes that allow me to select various things I'm looking for.
For example, do you care if your cover art is at least a certain size? In my case I had some very low resolution cover art, in the neighborhood of 250 x 250. These looked kind of terrible and I wanted to replace them with larger (higher resolution) images. My view let me select everything with cover art below a certain resolution.
Here's a link to a thread talking about this subject, with a screen shot of my Cover Art Review view. A few posts down I have an exported view that you can import into MC. The import process is weird and takes some figuring out, but it can be done.
https://yabb.jriver.com/interact/index.php/topic,98325.msg701887.html#msg701887To answer the easiest part of your question:
To search for songs (files) without any images:
[image file]=""
You can paste that right into the search box. Or you can make it part of a Pane that has embedded queries.
Best of luck to you.
Brian.