Being the tech-savvy crowd you are, we figure you use most or all of the standard Windows hotkeys, such as Ctrl+C for copy. It's also probably safe to assume that you break out the command prompt once ...
Copy an image to the clipboard. Navigate to a workflow containing an "Image File Node" (also referred to as "Load Image" node). Select the Image File Node. Press Ctrl+V (on Windows/Linux) or Command+V ...