Thumbnails

“Use thumbnail sketches to explore layout options. … are rough drawings, sometimes only comprehensible to the designer. … quick pen or pencil sketches allow the designer to try out … ideas and zero in on the most likely layouts before beginning a project.

Creating thumbnail sketches is a crucial part of the brainstorming aspect of your design work. Don’t discount the value of this step in the design process. …

Designing with Thumbnail Sketches
Don’t fret over details. Use thumbnails to establish approximate locations for major elements. (the examples described above may actually be “too perfect” — don’t worry about making “pretty” pictures.)

Try for an approximately proportional …. size… You’re aiming for a general idea of how the piece might look.

Make lots of rough sketches. Repeat: lots of sketches. You’ll rule out many design ideas quickly this way before wasting time in your page layout program.

http://desktoppub.about.com/cs/basic/a/thumbnails.htm

Thumbnail sketches
“Art directors and graphic designers use the term “thumbnail sketch” to describe a small drawing on paper (usually part of a group) used to explore multiple ideas quickly. …

Etymology
“The word “thumbnail” is a reference to the human thumbnail… and alludes towards the small size of the image or picture, comparable to the size of the human thumbnail.”

http://en.wikipedia.org/wiki/Thumbnail