I ran into this issue on my Horror Challenge Post (see sig for example).

Pm Guarddog, he got pretty darn close a couple of times.

Did you resolve this by posting a Part Two?

Ordinarily, given the board software's apparent constraints, I'd suggest that you include a place-holder right after your initial post in such a thread. That way you can edit it when you hit your head against any image limit in the original and they are right next to each other.

I've no idea whether the board software is smart enought to different between images posted using HTML and those using the "in-house" image tags.

I tried both [img]imagelink[/img] and <img src="imagelink"></img> tags in one of the "Guess That Moive By Screenshot" threads, and couldn't get either one to accept more than 25 images in a post. I "faked" the look of five images by 'chopping them together as one with white borders between the images and adjusting the captions below accordingly.

So in my experience, no.

You could host a page off-site and bring it in via an iframe.

We really don't want people to use that type of method as it has a lot of potential for abuse. Spammers try to do that to embed referrals and other things.