Exists Multiple Images

What is the fastest way to determine if any one of say 30 images appear in a region.
At present I loop through all the images with exists(Image,0.2)
Is there a better way.

n.b. Random number of images - if it fails to find one then my code takes a snapshot of the image and adds it to the list to find.
So code starts off with no images to find and expands with the snapshots.

for loop
      Image = the file name of the snapshot taken
      if exists(Image,0.2):
          return image info
not found so take a snapshot