@Anna W. 

There are 2 ways that I can think of right now how you can do this..

• If you have a list of people who already submitted the photo.. create new List, add those people to the new list and then in the segment add definition “If someone is or is not in a list - Person - Is Not - in list X (where list X would be list you previously created and uploaded those people in)”
• Or the second option is if there are just a few people, then you can add definition to the segment: AND  property about someone - email - doesn’t equal - the email of the person you want to exclude from the segment (but take in consideration that you would separately need to do this for every person you want to exclude, if there are 10 people you will have to repeat this definition 10 times for all the 10 different emails)

Thank you so much - Will try your first suggestion!