If they are old image they most likely died on the move, and the reason is that the new server is NOT case sensitive, so in the new server deathNote.jpg and deathnote.jpg are exactly the same. However, on the old one, these were different. The gallery had a system in which if you are uploading an image and that image name already existed, the new upload would get a (2), (3)... attached to it.
The problem came when we moved and some of the images ended up with the same name. When this happened, one of the two images got deleted and it does not show anymore on the site. I will be deactivating these images as I find them and fixing them as soon as I can. (Yes, they can be fixed because I have a complete backup of the old server), but it will be a while.
This will never happen again, no matter how many times we moved, because now, all images get renamed using the imageID, which is unique, so it is not possible to have to images with the same name (but different case). However, any old images that had this problem with not show.
For that second set of images, I guess they got corrupted on the transfer. I will fix those too.
Please, keep posting those that you find and when you click on a link and it takes you to the home page, it means that they have been deactivated and will be fixed...
Thanks a lot for all your help.