i=0; for x in *.jpg; do cp $x "image_$i.jpg"; i=$(($i+1)); done
The above command will copy all jpeg files in a directory and give them a new name with an iterating numerical value.
So if you had five images in a directory: bird.jpg, cat.jpg, dog.jpg, fish.jpg and hamster.jpg
Executing the above command in the directory would create an additional five images named: image_0.jpg, image_1.jpg, image_2.jpg, image_3.jpg and image_4.jpg.