I'm also looking for the same functionality in Mp3tag - the ability to display the cover resolution in a column. However the solution suggested at Cover Dimensions - another approach is way to complex and impractical, and the idea of using another app, or exporting the images to Windows Explorer, defeats the purpose of having a great program like Mp3tag to manage our tag data. I'd like to be able to view this info without having to install and use other apps.
Obviously Mp3tag is already capable of reading this data - the resolution is already displayed there in the Tag Panel, along with the image's MIME type, image file size and cover type. And it's already possible to add a column for the MIME type, size and cover type right now. All that's missing is the ability to add the resolution as a column.
Is there a technical reason that this is not possible?
If not, is there any way to suggest this as a new feature to the developer? The best solution would be having this added to Mp3tag so we don't have to rely on external solutions - and this will only further help Mp3tag to continue to be the best tagging app available!