It seems there's a bug in the drag and drop functionality in Umbraco 7.2.5. When I try to drag one or multiple images to the drag area, its center icon and text will flicker, alternating between the default "Click to upload" and the "Drop your files here" text (the accompanied arrow and parachute icons flicker along). The drag and drop functionality won't trigger, instead IE will load the image file (and change the URL to your local file path, replacing the Umbraco environment in the tab).

I could not reproduce this error in Chrome or Firefox, it seems to be IE (11 in my case) only. I've tried a local 7.2.6 installation and encountered the same problems. I've also tested IE9 but it seems the drag and drop functionality doesn't support that.