How do I get ALL of the gallery images for Lux Pain?!?

I've played through the entire game but I'm still missing 19 images!! And the ending I got was terrible... you just defeat the main boss and then everyone congratulates Atsuki and it goes to credits... so I'm hoping that there are other endings because that one was stupid!! And is it possible to have Atsuki get with any of the main characters?? If so can you please give the steps on how to do this or give me a link that tells me how?? :))