You can copy and paste, but only when using the HTML editor. The basic editor is just for text, the HTML editor will convert the picture in the Clipboard into HTML code so that it displays as a picture, like below:

But it's not "cool," as the picture will be in bitmap format, i.e. huge in size, not optimized as a .jpg or .png compressed file. Switch back to the basic editor and you'll see how this small screenshot excerpt is rendered in text form, it is very impressive. It basically contains the color number of each pixel from column to column, row to row.

As for dropping the picture from the Clipboard or Windows Explorer as a file, it would require a bit of programming, and the NAT admins are volunteers with little time on their hands for such work.