Thanks so much for the kind words. We had a great time sharing and it was really fun to meet you in person. Let's see what we can do to help you forward with your ideas.
Multiple photos in a plaque
You could attach the photos into a longer image file (any image will stretch to fit the width of the screen, be set at the top, and can be as long as needed), you could make several plaques, or you could make sure the photos are hosted on the web and then insert them via html (<img src="" etc.) into the plaque's text.
Video or animated image in plaque
these work just like regular images. Just upload them into the media tab. Check the "autoplay" box depending on your intent. It can be a bit of work making sure your video is reasonably small so that it downloads for players in a good amount of time. Advice for that depends on what hardware, software and experience you have with video.
Lock based on Survey completion
Without getting deep into web coding, you can't lock based on a player's completion of an online survey, but there are a couple things you can do that might be close. Say your survey is online like a google form. You would create a webpage object and use the form's url there. You can lock other game triggers based on your player seeing this webpage, just not whether they do anything there. Or at the end of the survey, you can give them a secret code in the "thanks for participating" message. This code then would correspond to a QR code trigger (but entering text instead of scanning an image). That way, they would really need to complete it or get the code from someone else.
Another possibility is to use conversations to create the survey itself. Then you can easily lock the game based on whether they respond. But you wouldn't get results from them taking the survey like you would in google forms.
Lock based on image uploads
There is a lock type called "player has already" "created note with media". You can use this to gear game progression to whether (and where) players add notes to the notebook. It's a bit hard to playtest as an author though because when a player "resets" their progress in the game, this does not reset their notes. It is not possible for a player to go back in time to when they have not yet created notes. I get around this by creating dummy accounts to test through. ARIS can't know what's in the photos either. But just as with the "secret code" from the survey, you can ask players to pull information from the environment (use a QR code type trigger but have them enter information into the decoder).
Hope this helps you keep going. Stay in touch!