Multiple images no longer appearing

What's the rule for merging? Do I just merge all files that I see that are different?
I already posted how/what needs to be done - then only the files from that list that you have custom template versions
kobra:

You will need to compile a list starting at your current version to the version you are upgrading to and list the files changed between each version into a single list
Each version has a change log

Do I merge from left to right (1.3.8 to 1.3.9)?
Again Only customizations need to be merged into the 1.3.9 files

Coming in late and haven't picked over the detail in every post, so apologies if I'm slightly off target ... but I don't think the problem is in the upgrade, but rather in the way in which your custom changes were implemented.

I suspect that changes were made to your template_default files directly and then got overwritten by older (not newly changed) Zen Cart files during your upgrade.

That's sort of what Kobra's getting at when he talks about the need to compare files to find changes.

Unfortunately we can't see from the public side of the site precisely how the changes were effected. But I'd start by looking at your template_default/templates/tpl_product_info_display.php file.