Let's start with the most important question:
How do I get hold of the Worldforge media?
We host all of our media on a Subversion server. For a quick peek it through a web browser at https://svn.worldforge.org:886/svn/media/trunk/. However, what you probably want is to sync everything locally. Use an Subversion client for this. We provide more information about this on the Media FAQ page.
About the media
Worldforge has a very large and diverse media repository. We're somewhat unique in that we offer such a large quantity of media using Free Software licensing (GPL). Various asset creators have contributed to the repository over the years. It contains meshes, textures, sounds, music and other kind of media assets. When using the Ember client to experience the world, every graphical element you see and every sound you hear are provided by our media repository.
The first thing you must be aware of when contributing to the media repository is that we require that all assets are licensed under both the GPL (version 2 or later) and the GFDL (version 1.1 or later) license. By experience we know that artists often aren't aware of how these licenses work, so do read through them.
Once that's done you should start looking at the existing media. We want to provide various games, but our main example game is set in the Dural world, which is a medieval setting. To keep things simple we've set a naturalistic art direction. It's just easier for everyone if all assets strive to be natural looking.