Imagine you draw a small rectangle that could easily fit into a matchbox. Then you sketch a very simple shape for a character inside it. Now create a second rectangle directly next to the first one and slide that same character so they’re just near the border. And in a third rectangle, draw a larger version of the background with a smaller character inside. In each of these cases you don’t need a finished facial expression, a polished line drawing or even a nicely rendered background. You only need those rough rectangles to show how fast the mood of a book page changes when you vary where the character sits on the page, their scale and the negative space.
Thumbnail sketches are handy as long as you’re working small. If you’re working on a large drawing, moving the character or background or trying out a few different angles of the illustration can feel hard to do. If you’re only doing a tiny thumbnail, you can play with those basic ideas before falling in love with any one detail. You can use a few pencil marks to ask: does the reader’s eye go right to the focal point of the scene? Is there enough space to put text there? Will the reader feel comfortable with the turn of this page, or will they be surprised, or frightened, or sad, or all of the above?
A common trap for new book illustrators is skipping the thumbnail sketches and moving straight into “the real thing.” The problem there is that a full-page illustration has so many decisions all at once, and they can be overwhelming. Think about the character’s pose, the character’s expression, the character’s props, the setting around the character, the layout and margins, the balance of values, and the eventual coloring. That’s a lot, especially when you’re in the middle of the page-making process and just trying to get one thing right. A tiny thumbnail sketch has most of those decisions left out, leaving you with just one big question: what is happening in this scene? A thumbnail can give you just that, and in just a few minutes.
Try doing a quick thumbnail sketch five times of the same page. Don’t just redo the thumbnails you like, though. Do each one as if it were a brand new illustration. If you get stuck, do one with a full two-page spread with the character small and a roomy background. Then do another where the view is close up on just the character’s hands, opening the gift box. Do another with the character on one side of the page and a big open space on the other for the text. These variations are important because you don’t get one finished illustration, so it’s easy to compare them against one another and learn from your own changes.
Your thumbnail sketch doesn’t have to look like the end goal, it just needs to have a good shape. Use simple silhouettes for the character, block out big masses in the background, and lightly mark out text area. If every part of the drawing inside the page is roughly the same scale and weight, you might not have a very strong page. If the background mass is heavier or darker than the character, your focal point is hidden. If there is no place for text other than tucking it awkwardly into the leftover space, that might not make for a good layout.
One more great use for thumbnails is the way they minimize the pain of changes. It’s a lot easier to accept the criticism of “this version doesn’t highlight the main action as well” than “that drawing is completely wrong.” Book illustration is all about changes and revisions; making thumbnails is just another step in that journey. A good thumbnail can be tossed away, circled and improved on, combined with the next thumbnail, or just used for a specific detail inside the final drawing.
So before you take a thumbnail sketch to a final draft illustration, ask what is the single most important part of that page? It’s the thumbnail that allows you to see a clear version of that page beat. It’s the draft that you feel has an obvious path for the reader’s eye. It’s the drawing where the text has just the right amount of space. That tiny little thumbnail has done its job once you pick the draft that makes your next page feel less like an open field and more like a solid plan.