Hi! Thank you so much! :)
I've had a look at the CG's in question, and I think that 2 of them are probably the CG's for Endings 1 & 2 which are somewhat jokey endings that can be unlocked by consistently choosing certain types of answers. I'm not sure what the 3rd missing one is however. The remaining ones after are all from the Halloween update, so I'll have a look if there's maybe a small glitch with one of them :)