Free images results:

Cracks pictures, stock photos and images


Cracks 2 Royalty Free Stock Image
Author: Viking
Crusty Stock Photography
Author: Lisajames
Knot Royalty Free Stock Photos
Author: Jxpfeer

Also, here are some commercial RF-licensed images that match your search criteria:  
Cracks Stock Photo
Author: Theodor38
Mud Cracks Stock Images
Author: Gregc