In working with words and images in book form, how do you decide what is the right number of images to use? Someone said he wanted to work with fifteen images but didn't want the finished book to look like a photo album or scrapbook. Is fifteen too many? If the images were scattered throughout a 200 page book, I'd say not at all. But let's say you want to make a book that can be read at one sitting. Fifteen is a lot to take in, unless the images are sequential.
Part of what makes a book special is the concept of memory. Every time we turn the page we have to remember what came before, and not just what immediately came before, but everything up until that point. According to early studies of working memory capacity, it was found that we only remember seven things at a time. That idea has been expanded, depending on the category: seven numbers, yes, but we can also remember other things in about four chunks, each chunk comprised of several things (apparently we can remember more short words and fewer long words, for example.) So perhaps we should approach sequence and ordering in chunks! For our purposes, let's make these chunks smaller than conventional chapters.
It is possible that fifteen images could be used if they were grouped, and particularly if each image in a group had a relationship to the others. I would argue that anytime you put two images side-by-side you will subconsciously want to link them.
A conversation begins. Now what if you add a third party (or took out the second one?):
A conflict is set up. Or a turn in the conversation. A bit like six-word stories, but in this case each image stands for two words. Something changes and builds. Our eyes dart around, trying to help us fill in the conceptual gaps, searching our experiences for similar scenes.
If you must use fifteen images you could continue adding them, creating layers and complex connections. As the pages turn, the images would stack up in memory to create an overall effect. You could also create several (three to five?) grouped chapters and leave space or put a story, poem, or dream between them. Try varying the number of images or the length of the writing. The reader's mind can now hold one idea at a time in a deeper form. Adding words that convey an impression of mood, tone, or conceptual qualities would be more effective and interesting than writing a literal description, I suspect. If the images are sequential, the final impression may be simpler: the reader can hold the basic idea but may not have to remember the details. If you have sequential images, you could alternate between a story told in words and a story told in images; a wonderful example of how this works is in The Invention of Hugo Cabret by Brian Selznick.
Words and images do different things when you look at them. I notice that after turning a few pages of a purely visual book I begin experiencing it as if I were floating on my back in a warm pool and my ears were partially submerged. When I get back to words I hear voices in my head again: they feel much louder. I love verbal language, but sometimes it's nice to have that quiet, wordless space to move around in for awhile.
(For a visual poem, mostly comprised of linked imagery, see the 2010 film Somewhere by Sofia Coppola. For music that may put you in that warm pool or even to sleep, listen to "Weightless" by Marconi Union.)