John,
I moved this here and started a new thread so as not to highjack the Hotchkiss thread and because it wasn't really related to artillery. I hope you don't mind.
I am the webmaster technically although I do bring my son on board to help when I don't have a clue or when I have no bandwidth. Neal has been an incredible asset for me. But with regards to your question the short answer is no. I've looked all over and seen nothing even remotely related in the forum configuration. I also searched the web and found nothing. Additionally I tried a few posting tricks to see if I could trick it into adding the scroll bars.
One way you can ensure a scroll bar for each image is to only include one image per post. Start your post or reply and add an image. Then immediately add another reply with the next image and so forth. They'll essentially be in order the same as if all in one posting but each will have a scroll bar.
Please note that the only one who will see any scroll bars to begin with is someone who has a small monitor, views the forum in a small window or has set their monitor to a low resolution. Or it could be some combination of the three that causes the need. I, for example, never see them since I have pretty decent size monitor and use a larger window.
I hope this helps.