Getting next ID before insert

[eluser]Pert[/eluser]
Another option is to save image files with temporary random unique filename, if there are no errors, create DB record and then rename files to use new ID.

If thumbnail generations fails, you won't end up pushing ID higher and higher, but that's probably just personal preference

Depending on the images, it would also be easy for someone to scroll through all the images by just changing ID number on URL.