great idea, but it seems rather than attachments, most users these days just paste links to external images (which IPS thankfully auto-embeds)...
therefore, i was going to ask if you might add support for using the first embedded image. however, i just read that Facebook and possibly other major social sites will be enforcing that the og:image URL be from the same domain as the page (or a white-listed domain) - so i guess adding such a feature would only be practical if our site was using the IPS cache-remote-images feature.
so instead - would you consider adding a way to specify a fallback image per-forum for when there are no attached images on a post? then at least we could have an image that is more appropriate to a particular link than our default site-wide og:image.
thanks!