If you had completed all of the characters' events, you'd have the Gallery filled out.
Click the info tab and see who is left.
Most people don't finish Lucia, Moon or Nia's events.
2 years ago(-1)
I already finished them all.
I've also attached which scenes are missing if that helps.
2 years ago(+2)
Click the "i" button at the top of your screen, that will tell you where everyone's story is at. Those who aren't maxed would be the one you're missing.
I don't see anymore of the "i" indicator. Are the two missing scenes related to Nia and Sylvia's Love and Slave route?
I first played the Love route for the both of them and there were two scenes missing, I used the cheat code for it to turn into the Slave route and there were still two scenes missing. Please check the screenshot attached to this reply if there's something I'm missing. 
2 years ago (+2)
You are missing Vanessa's events.
Visit Kali at Syltech in the evenings, and feel free to visit her wiki page if you need help with her events.
https://harem-hotel.fandom.com/wiki/Vanessa
325 days ago (-1)
how do you visit nessa? i dont know where to click to visit the college, the option is removed from kalis door but is there anywhere else? if youve completed the college part do you miss out on nessa? thas unfair, it wizzed by without giving me much chance choice or warning
325 days ago (-1)
The option is on Kali's door in the evenings (weekdays iirc), as stated already. She hasn't completed college yet as far as I've played (v0.16). You can't miss out, the game is pretty much designed that way.
Only things to "miss" are major choices made very clear to you, like Slave or Love Route for Nia and Sylvia, which you can just save before that choice, load a save, or load an autosave if you saved over. There's also a cheat for Patrons to reset the route should you wish (before you ask, I'm not a Patron anymore).