You can create collage pages with more than one photo per page in your Classic book using the Chatbooks app on iOS or Android.
How do I make a collage from photos already in my book on iOS?
Tap your book
Tap the photos you'd like to collage
Tap Collage
Change or replace photos if you'd like, then tap Done
Tap Done again
How do I make a collage with new photos on iOS?
Tap the + in the lower right corner
Tap Collage
Select the number of photos you'd like in your collage and continue
Change or replace photos if you'd like, then tap Done
Tap Done again
How do I make a collage on Android?
Tap your book
Tap and hold the first photo you'd like in the collage
Tap the second photo
Tap Collage
How do I edit a collage?
Tap the collage page, then tap Edit Collage
To turn the photos back into individual pages, choose that option here
To crop a photo or swap it for a different one, tap the photo
To move a photo to a different spot in the layout, tap and hold it, then drag it
When everything looks right, tap Done