All Thumbs !
Thumbnails are drawn thoughts. These small sketches, combined with brief notes, capture ideas for a story or character so that the memory is not lost. Thumbnails can be worked up into a finished drawing at a later time.
Always work rough before going clean. Do not render or model final drawings at this stage. Draw a new thumbnail if you can stage something better. Thumbnails allow you to change the drawings and your mind.
Remember character designs and storyboards both start out as rough and simple thumbnails. And for Animators they can portray different stages of the animated action.