Symmetrical faces
Here's an idea I just saw on Flickr:
Even though it's supposedly part of the ideal of beauty, no-one has a symmetrical face. This means that taking a picture facing the camera directly allows one to create two half-clones: the left half, mirrored, and the right half treated the same way. Both are recognisably derived from the original person, but neither actually look like them. Rather than looking more beautiful, they look a little creepy from being too 'perfect', or at least too regular.
I haven't yet tried this myself, but here's a triptych from someone who has.
Even though it's supposedly part of the ideal of beauty, no-one has a symmetrical face. This means that taking a picture facing the camera directly allows one to create two half-clones: the left half, mirrored, and the right half treated the same way. Both are recognisably derived from the original person, but neither actually look like them. Rather than looking more beautiful, they look a little creepy from being too 'perfect', or at least too regular.
I haven't yet tried this myself, but here's a triptych from someone who has.