We recommend a ratio of 4-6 images per every one sheet. Of course you can supply more or less images and we’ll gladly accommodate but we find this ratio serves as a good average.
This question also depends on the size of your images. In general we find a few large images per a page make for a more enjoyable layout than lots of smaller images. You’re free to specify how many images per a page you’d like us to use.
You can also supply us more images than you want used and then have us pick out the best images. This is often easier for professionals who have an idea of how many images they want but don’t want to take the time to individually select them beforehand.