In the 2nd level, Count Olaf's house, once you reach the Kitchen, you can rack up photos rather quickly. At the far left is a tall cabinet. Go to the top and jump
right. Continue jumping along the platforms to get about 10-11 photos. Leave the room, come back, and they'll be there again. You can continously do this.

Also, after fixing the broken window on the right, you can get 3 photos from that
platform every time you enter too. That means about 15 photos every time you enter. After about 60 times of collecting photos this way, you can have about 900 or so. It is a little time-taking though, so be patient.

NOTE: This may be available in other areas.
NOTE 2: Instead of exiting via the door and coming back in, you can just switch to Sunny and go in the Cold Storage and exit back to the Kitchen. That
way is quicker.