Recently, I attended a CBIG meeting on Jan 11th, our guest speaker was NW, Assoc Ed from a medium sized NYC trade publisher of Books for Young Readers. Sorry about being so mysterious but some info is proprietary to CBIG. Nor would I want to incur the wrath of NW! Here's what I learned from the meeting that I can share with my fellow children's picture book illustrators/writers:
3 types of End papers and how they effect the Picture Book page count.
Self-Ends: Illustrated by the artist & are counted in the page count. They are printed on the same kind of paper as the interior of the book. They account for 8 pages in a 32 pg bk. Pg 1 begins on the side that's actually glued into the hardcover. Pgs 2 & 3 are the actual illustrated front endpapers. Pg 4 maybe left blank, maybe illustrated, or the © info may appear here facing the Title page on pg 5. Title page is on pg 5. Story starts on pages 6, ends on page 29. Pg 30 & 31 are your illustrated back ends and pg 32 is glued into book.
Colored Ends: Colored paper inserted in book. Not counted in page count and are different stock than the interior pages.
Printed Ends: Artist designed/illustrated but on different stock than rest of book and maybe 1 color vs the full color interior pages. They are treated as Colored Ends and aren't counted in the page count. Rarely used nowadays.
8 x 10 is the most economical size for a PB: PB's are printed on large sheets of paper in signatures of 8 pages. They are then folded, gathered and trimmed. The 8 x 10 size allows for the least amount of paper waste on the most commonly used paper size.
Storyboard your Book dummy. Helps you to make sure art & story isn't static.