If your pictures have been in the same location (same folder, same subfolder, ...) for more than a week, then copies if them will remain in your TM backups until it fills up. They are then vulnerable to being deleted.
If they've been there for less than a week, TM could delete them as early as a month from now. If they've been there for only a few hours, chances are TM will delete them tomorrow.
This is why TM is not the best tool to use to archive data that you will be deleting from your main hard drive. Copy them to a dedicated external drive, or burn DVDs.