This tutorial describes the steps that we recommend to create a new map for extraterrestial bodies in Marble, like other planets, moons etc.. Using Marble doesn't limit you to view maps of the Earth - you can choose to create maps for any celestial body you like. So you'll be able to display the celestial bodies in all of the projections that Marble supports. And by creating these maps you'll be able to leverage from most of the features that have been implemented for the Earth already. However this also holds one limitation: Since Marble's rendering engine is based on a number of fixed projection types you can only get a "realistic view" for those bodies which visually resemble a sphere: So bodies like Jupiter or Vesta which are either visibly oblate or where the shape deviates significantly from a sphere can not be visualized in a way that matches their actual shape. In future versions of Marble this limitation might be removed once Marble supports OpenGL based views.
For your private projects you can create Marble maps from any data where the license fits your needs - no matter whether the map data is free or proprietary. However if you want to contribute your map theme back to the Marble project - which means that your maps to be distributed by the Marble project you need to keep the following in mind: In the Marble project we want to support free maps - especially those maps which are licensed in the same spirit as the LGPL. This means that there should be no restrictions like "non-commercial" (which is a very fuzzy term and could actually prohibit usage of the map in a planetarium show or deployment on a linux distribution). So if you want to contribute your maps back to the Marble project please stick to e.g. "public domain" ("CC0"), "CC-by-SA" or any usage terms that don't make any requirements apart from attribution.
You must first decide whether you want your map theme to be visible for all users or only for the local user. Depending on your decision, the table below tells the path for you new map theme: