This has to do with Windows paint messages. Moving an application window across a hung application window causes an interesting effect. Windows will draw the un-hung application window and it is up to the background application to redraw whatever is exposed. If the background window is hung, it is too busy to process a move event. Done at different speeds, it is fun (especially while waiting for the stupid hung application to free up) to move the front app window across it to produce mountain ranges, slides, or whatever. I have not heard of a gallery of this kind but there should be. I kinda like it... Here is an example--

- Hung Art Gallery -

Blue Cliffs with Dopey Paper Clip
	Cliff Trail in Blue
Mount Azure
	Slide Park
Rapsody in Blue
	Blue Jumble