First, you shouldn't need to use a custom renderer to show an image. The functionality is built-in. All you need to do is return Icon.class (or ImageIcon.class, either works) from your table model's getColumnClass() method.
Second, what do you mean by pasting an image? If you mean pasting from the clipboard (a la Ctrl-V) then it will take a little work. It would probably be easiest to create a class to pass to setTransferHandler().