Hi there,
I was discussing this with a dive buddy of mine yesterday and hadn't even realised it's an issue: while it's possible to add pictures of a dive site, it doesn't seem to be possible to add pictures of a dive, such as u/w pics, pics of the dive group, etc. Has this been considered as a (future) feature? Obviously, syncing would need to be implemented, too, so that entry on the Mac and viewing on iOS devices is possible.
We have certainly looked at adding "per dive photos" to Dive Log Manager/Dive Log DT and Dive Log on iOS (in fact, there is already some support for this feature in the logbook database schema that we use). As you point out, synchronization between the desktop and iOS needs to be implemented to which is not an insignificant task. Up to this point in time, the biggest impediment has been how photos are handled on iOS. However new support for photo handling in iOS have given us some new options.
So, the short answer is that we are looking to add this in a future version of Dive Log and Dive Log Manager/Dive Log DT, but I don't have a specific time frame to offer at this point in time.