Some photo-viewing apps already provide this and I find it very much helps you focus on the image/s at hand, whereas the Windows border can be pretty distracting (the way it usually works is for the border to be auto-hide when the cursor is moved from atop the app window). As far as I can tell, it shouldn't be too difficult to implement and it would be a welcome addition to the CDX feature list
Take for instance this image which was taken using the Image Eye app and background dimming software (makes the desktop dimmer than the black you get during full screen)
http://imgur.com/a/Ptkx7.
Anyway, hope this can be considered. Thanks and keep up the good work
