Mark at all is currently not implented. The issue with that I have to add an entry for each picture in the gallery to the table for the user. Which could be a ton. If there are 4000 pictures it would add 4000 rows to to the database and that would take a very long time to do.
Thank you for your quick reply
OK, I think you mean this:

1000 users, 5000 pictures.
So, if I would mark all as seen, for 1 user, would it be 5000 entries into the database.
For all users would that be 1000 x 5000 = a lot.
This is what you mean?

Vincent