Ive noticed a few folk having issues with pictures becoming “randomised” and not in the intended sequence. Ive had similar problems on another forum, I found that if you rename your pictures 001, 002, 003 etc…. when resizing, and continue like this all through your thread, then they seem to appear in the correct order. Hope this helps.
We have discussed this issue with the site developers and they confirm that the randomisation is in fact the software of the website putting images in alpha/numeric order, so Darrens solution should work.