All pictures have been found
All related pictures are in a separate folder for the 'master' picture. For example, the four pictures that, combined, form a house are all in the same folder, perhaps named 'house'.
A consistent naming protocol has been applied to all folders and files in those folders. The protocol should be consistent across folders. Consider upper vs lower case, spaces vs underscores, CamelCase, numbers, extensions, and other possible elements of a file name.
Whoever finishes first gets two bonus points, but those points can easily be lost by poor naming or file management.