Maybe you come up with completely original characters out of nowhere. Maybe they are based on no one except the fully developed, multi-dimensional they are. Maybe you are content to have your book exist as the written word and nothing else. Good for you. I…am a different type of author because I absolutely want to see all my characters on screen. In fact, to me, there is nothing more fun than finding a person (in real life) or via current actors / models that is the *exact* version of the character I had in my head.
In a former life, I’ll never forget being with a group (I was a tour director) and after meeting everyone, I realized one of the members was identical to how I pictured a character from my YA series. Not wanting to seem a stalker, there was no way of me marching up and saying, “Hey you, the one who looks like Drew, mind if I take your picture?” So, I just had to try and control my grin every time I saw him. Since then, I’ve been fortunate enough to cobble most of the cast from YA series, unfortunately, many of my original choices have now grown past or aged beyond the role I had initially mentally cast them for (I’m looking at you, Molly Quinn and Ellen Page).
I haven’t been so lucky with my other works in progress. I actually think the latter is a sign that I’ve not given enough thought (or words) towards the respective casts. While having a picture (not in my head) isn’t necessary to writing or developing a character, I do prefer having some reference when possible.
One last note, when “real people” fail, there is another option. While I’ve not played Sims (at least not for years), there are a number of online websites where you can build your own superhero or character.
Until then, the search continues…