sending multiple emails

I think the only way is to write on the public comments at the bottom of a pic. Those who already commented on your pics are alerted on their news page that there are more comments. The only problem is having the time to check through all the new comments. I certainly don't manage to do this.
Private messages of course are easier to spot and I always manage to read these, but they are sent singly.

Your could write a blog and choose a suitable heading to attract attention. :o)

try and think of a way of making it a question .or ask a question and thank everyone after you have finished your question