Free images results:

Alert pictures, stock photos and images


Hydrant Royalty Free Stock Image
Author: Ichtor
Falcon Stock Images
Author: Folderol
Lizard Royalty Free Stock Photography
Author: Pilarin
Black buck Stock Images
Author: Plsa

Also, here are some commercial RF-licensed images that match your search criteria:  
Alert dog Stock Photos
Author: Miele

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