John Lee said:
Isn't it kind of obvious? I'd place appropriately resized screencaps of both sites, and caption the Goatse one "Goatse is one of the most commonly used shock site on the internet" and the Tubgirl one "Although not as commonly used as Goatse, Tubgirl is also used on a regular basis to shock unsuspecting users".
Size is important. A postage stamp picture of Tubgirl or Goatse would not, in my opinion, be likely to shock many people, but it would give them an idea of what to expect if they clicked to see the picture full-sized.
Not all people would care to have to click a few times every time they visit a webpage just to view its images.
This only applies to those pages where you choose to suppress image downloads.