If you want, I can:
: Higher-end skins feature finger-motion tracking where the character's eyes follow your touch on the screen. Community-Made External Viewers
A "full" viewer typically offers the following functionality:
The biggest selling point is camera control. In the game, you are stuck with a fixed perspective. In the viewer, you can zoom in to see brush strokes on the art or zoom out to see the full composition. You can rotate the model (where supported by the rigging) and adjust lighting parameters to appreciate the shading details the developers hid in the default settings.