is there an option/mod to create the normal_ and thumb_ pics 'on the fly' if they are missing (e.g. if a find -atime -exec rm removed them after n days to save some space or a disk crashed and the backup was played back etc...)
No, but you might look at the in the fly watermark mods for some ideas.
thx... I think I'll just write an apache-404 exception handler to handle the missing thumbs... and I can save the the overhead to always stat()