Free images results:

Gravel pictures, stock photos and images


Wine on road Royalty Free Stock Image
Author: Mhd
River Stock Photography
Author: Red2000
Pebbles Stock Photography
Author: Ichtor

Also, here are some commercial RF-licensed images that match your search criteria:  
Gravel Stock Image
Author: Jeephade
Gravel Royalty Free Stock Images
Author: Uko_jesita