I tend to do alot of screenshots to save images as PNGs to review later or save as information for use later [as in showing someone how a certain file structure or window should look if you're explaining to them a process]. Thus, every now and then I do have to go thru and clean off the desktop of my computer. I have all sorts of 'Picture #.pngs' all over and there's really no reason to keep them. So, I open QuickLook [keystroke: click on an icon and hit Command & Y - to close it do the same keystroke] and see what the icon represents and either delete it [just hit Command & Delete/Backspace while it's open in QL] and then click onto the next icon, without opening or shutting QuickLook. That icon will then pop up so you can see it also.