Many ideas to modifications and expansion casings have been posted on the wiki's discussion and on the mailing list. As the CAD-Files of the original case are freely available there are two kind of expansions;
- complete back covers
An existing expansion is a DAB module inside a "extension back", created for the Openmokast project. While a custom back cover would both cost much more to produce via rapid prototyping and destroys the design of the device, this extension will fit inbetween case and cover.
The CAD-File is available for download at http://openmokast.org/cad-files.html and is suitable for other extensions, such as a larger battery or hardware housing.
Ideas and CAD Files
An eager project is http://wiki.openmoko.org/wiki/Wishlist/Expansion_Back with several good ideas for multiple extensions, while staying modular.