Abrosoft FaceMixer is described as 'is designed to create fantastic face composite with multiple individual faces' and is an app in the Photos & Graphics category. There are five alternatives to Abrosoft FaceMixer for a variety of platforms, including Windows, Online / Web-based, Android, iPhone and Android Tablet. The best alternative is Face Gen. It's not free, so if you're looking for a free alternative, you could try FlashFace. Other great apps like Abrosoft FaceMixer are Sketchcop (Paid), PortraitPad (Free Personal) and Faces ID (Paid).
PortraitPad is a web application for creating facial composite picture which is equipped with its own originally high quality features catalog. PotraitPad is created based on Microsoft Silverlight 5.0 technology.
It provides a palette of facial objects: eyes, jaw, hair, etc. For each, you pick the one you like, then place and size it appropriately. I thought the Flash-based interface was pretty clever. You can even save your creation.