Here's what I found out.. If you use size 8, you'll get those corners. If you use size 10, you don't because the image goes down. There's no way I can fix this. I can get the image right, but then the text (and other things) are off center.
MC repositions everything and offsets all my stuff. There's other areas where this happens, not just the display area. There needs to be a fixed size and the font then should center in the images. So until they fix it, I would use 10 point.
Other areas affected are: toolbar, action window, search bar
Redoing everything to 8 point would take awhile. If you do switch fonts, you will need to restart MC for everything to work.