Thumbnails can be
great for working
out large simple
images. Or even
large complicated
images like the NAIL
TPB cover...
... But most often I prefer to work them out at print size. Tracing
through the logo, if it is available.  



These are sketches for a Titan Books reprint of Alien Legion and
an issue of Aquaman.



This was a rejected Idea for the third issue of Another Nail.
There was also some concern about the title and my alternate
suggestions are above.

The other was intended for Marvel UK's Doctor Who book.
I will sometimes go back to working story pages out as thumbnails (if I'm
drawing a new book, new characters-- or just for a change of pace) but,
as writers tend to think crowds and armies are essential to every story,
working at a small size becomes counterproductive so I usually work on full
sized roughs or, if I'm feeling confident, directly onto the art board.