If you wonder to look at images with swapped faces and wish to do this trick on your own taken pics
Then go ahead, Face App is all you need.
Just take picture or choose any from your gallery and play with them.
Features :

Face Adjustment ( Use the Selection oval to adjust the faces).
Face Scaling ( Just touch any face with one finger and drag another finger anywhere on screen to scale). Face Rotation ( Select a face and use rotation slider to maintain the rotation of selected face).
Share on facebook, twitter, google+ etc