Not sure where to look to fix the broken links, if any. On the index page, only the featured image is missing (the recent added items are displaying thumbnails). The browse page are missing square thumbnails. On the detail pages, both the full size and thumbnails show up fine. I am using the Berlin theme (copied from earlier installation).
Did you move your 'archive' directory back into your Omeka installation after upgrading? If so, you might also check the server permissions on the files.
Huh! All the thumbnails are accounted for. I had followed your upgrade instructions with the archive directory and adjusted its permissions to 777. Not sure why the images did not appear right after the upgrade, but it looks like things are A-OK now. Thanks, anyway!
Awesome, glad they're working now!