In November of 2012 I was working on a major overhaul of the Steampunk novel. This was the one that took my mediocre second draft and transformed it into the novel I spent the next fourteen months querying.
Although the pull of NaNoWriMo was strong, I had promised myself to finish the rewrite of the novel and tagged along with a local group of eager NaNoers as they plunged into the mess and excitement of first drafts. Quite frankly, I was rewriting so much of my novel it was kind of like a first draft, but it was still technically a revision.
During one of my Sunday writing sessions, I asked the other two NaNo folks there that day if they ever used photos to help them build a picture of their characters. The response was immediate and dismissive. "No. I like to leave the protagonists appearance up to the imagination of the reader." And there was a kind of look they gave me. Like maybe I wasn't a "real" writer at all.
Quite frankly, I was puzzled. It wasn't like I described any of my characters in minute physical detail, but I found I wrote them with more emotion, more soul, more... character, when I could picture them in my head. And that usually meant that somewhere on my computer there was a photo labeled as Character X. For me it was, and is, a tool to help me connect with these people that I bring to life on the paper.
Over the years I've met folks who have complex soundtracks for their novels (songs for every character, songs for every chapter), who have massive collections of photos of locations, people, clothing, accessories, artwork, etc., even folks who draw their own maps and create a library of historical documents to build their worlds. And I've met folks who do none of those things. Folks who outline. Folks who don't. Folks who interview their characters. Folks who get their inspiration from dreams. Folks who won't write one word until they've completely researched every aspect of a historical period or a real-life place. Folks who make it all up as they go along and fill in the rest later.
And here's the thing: none of those things is the "right" or "wrong" way to go about writing a book. In fact, the only "wrong" way to go about writing a book is to get so bogged down in the periphery methods (inspiration, research, development) that you don't actually write anything. All those things (music, artwork, photos, maps, documents) are just tools. If they work for you then by all means USE THEM. If they don't, then put them aside.
Take what is useful, leave the rest.