At the moment, the way IP caches off-line images leads to compromising other website / server restrictions when it comes to hot-linking.
The two images here DO HAVE "NO" hot-linking at the server and functions normally with other forum / website software.
For example if you "Click" the images below - you get what you should only be seeing when this post / thread was submitted.
Whether you like it or not - This is serious, and in the current format that the restricted images are being handled could raise some serious objections as to the integrity of IP.
Edit:
Unfortunately I've had to revert back to squashing hot-link prevention for now for other reasons, but the fact of the matter is IP should not cache the "Preview Image" - rather it should cache the off-line "linked" image when the post / thread is submitted.