That is a tough question. I don't have a particular amount of pictures that I put on a layout. It really depends on what I am trying to say on my LO. For example, if I am writing a love letter to my daughter about the just one aspect of her personality or maybe I am writing down my thoughts and dreams for her, then I would probably just use one 5X7 picture. However, if I am trying to tell a story of the day's events or a holiday, then I may put several pictures on a LO.
When using several pictures, I love using premade templates for the pictures. And the best part...is that they are free collage templates.
They are very easy to use and really help many when I have 5/8/10 pictures I want to use on a page.