The Digimon Accelerator includes a new feature that allows you to change its design. This design is basically a thin piece of cardboard held between the DA and the clear plate that fits on top of it. The battery cover is located under the skin. With this feature, you are able to create your own designs and share them with other DA owners. There is a topic on the forums for you to post and look at others' skins here.
These are the official skins (Also called Design Sheets) available, including:
Creating your own skin