Free images results:

Yawn pictures, stock photos and images


Dog Stock Image
Author: Ichtor

Also, here are some commercial RF-licensed images that match your search criteria:  
Lion, yawn Stock Photos
Author: Pokec
Yawn Stock Photography
Author: Laozhang
Yawn Stock Photography
Author: Millaus
Yawn Royalty Free Stock Photography
Author: Soupstock
Pug yawn Stock Image
Author: Dreymedv
Yawn 478 Stock Images
Author: Bowie15
Woman yawn Royalty Free Stock Photos
Author: Mathom

Explore more commercial options: More Yawn Stock Illustrations & Vectors | More Yawn Stock Video Footage