If you are wondering what thumbnail sketches are they are small sketches which can help you work out a composition. Why bother with them? Well when we start drawing and painting we tend to forget that we have choices about what viewpoint, angle and the arrangement of subject matter.
Why Thumbnail Sketches are a Good Idea
Thumbnail sketches are essential to work out composition choices, they help the artist explore the options and what would work best before embarking on the final piece. You can explore variations by altering the placing of the focal point, the amount of background or foreground and different viewpoints. All this can be worked out before committing hours to a final piece which might not have the best composition.

Composition is important
Although the subject matter is important the positioning and viewpoint is what can make artwork interesting or not, so composition is worth spending some time on. You can play around with different solutions using thumbnail sketches. I always spend some time arranging a still life and working out different arrangements before I then start some thumbnail sketches.
Some questions to ask when trying out thumbnail sketches could be: Is the focal point (the most dominant object) in the right place? Is there balance in the composition, some small objects balancing out a larger object? Is it interesting? Does it lead the observer into the piece? Could the piece be cropped for better results?

Another way to find out what composition might work best is to use a viewfinder – see my post What is a Viewfinder? for more advice on this topic.