xD
Well, if you use Firefox, you could just move the picture from one tab, to this tab and drop it into the box (Move from one, to the other bassically).
Otherwise, you can just get the HTML (Right click, Inspect Element, copy/paste the highlighted text) and paste it in 'Source'. Or you could just simply copy the picture and paste it here.
Or you could actually upload a small picture to your pictures, copy/paste it. And then right click and resize it to make it bigger.