You could put the main file display into thumbnails mode, filter on images (push * and use the drop-down list that appears at the bottom for one way to do that), then use this script to display two selected images side-by-side:
That could be extended to show more than 2 with a bit of tweaking.
If you do it a lot and don't want to manually filter out non-images, a button hotkey could be made to do that very easily. (It could also switch to thumbnails at the same time, if you wanted it to.) Let me know if you'd like that but need help setting it up.