So you still have to be able to get all of the images selected by your mouse, in order to right-click them, yes? What if they are not all in the same directory? One false click and there goes your list. This highlights my points exactly. ;-)
But I will give it credit that the interface is probably (I can't check, I only use Linux at home and at work) not as bad as most GUIs. It's probably the best GUI you can create for something like this.
Oh, and it's Windows only. ImageMagick runs on many platforms (even Windows.)