Artists Guide

There are two main areas where we artists can contribute. We need 3D models and textures for the same and the landscape.

Textures

We use the CC-by licence for OpenClonk and ask you to license your contributions under the same license. As many textures in texture archives have licenses which are not compatible with CC-by, we will have to create many textures on our own. But don't worry, it's quite easy and there are some really good tutorials on how to create quality textures from photos:

How to create seamless textures

There are different methods how to create seamless textures, here is how I do it: Tutorial: Creating Seamless Textures.

For GIMP, there are two filters which can do this automatically: The plugin Texturize and the filter Resynthesise. Both work good with textures with small random patterns like gravel, plaster, sand or ground. However, they don't produce quite as convincing results for bigger regular patterns like (roofing) tiles, bricks, wickerwork, pavements etc.

How to create normal maps for textures

From photograph to normal map, how to... - Excellent tutorial including tips how to photograph right
Creating Normalmaps - Very practical but little background information

Texture archives

.... -> License issues, guidelines

Free / no Copyright / CC-BY

Here are some links to archives which offer textures "without any copyright", compatible CC licenses or public domain. Attention: If you want to extend this list, note that "free" or the lack of any copyright message doesn't mean anything. To be public domain or "without any copyright", it must be explicitly noted.

Flickr - mixed CC licenses
National Biological Information Infrastructure - good for mineral textures, public domain
LuGher Texture (3400+) - free to use in personal and commercial projects
Accustudio (~1000) - free of any copyrights
The Texture Barn (~500) - "Royalty-free textures for computer graphics, illustration, game design and everything else"
Texturenwelt (400+) - mixed licenses: see single images
Ben Cloward (~300) - free but author would like to be notified where it is used
Free3dsTextures (~200) - mixed Creative Commons Licenses - Attribution license would be compatible
Blender Texture Library (~200) - Creative Commons Attribution License 2.0

Mostly free with own license

The most and the biggest free texture archives offer the textures free for any purpose, but it is not allowed to redistribute them as a texture pack. So, in all cases, we need to print the license and copyright message with every redistribution. As this licenses for textures from these archives are incompatible with the CC-by license, we don't favour textures from these sources. However, we can still include them as long as we mention that these textures may not be freely redistributed by default. Before you contribute any textures of these archives, carefully read their terms and conditions as they all differ from one another:

CG Textures (30000+)
Image After (~10000)
Mayang's Free Texture Library (3800+) - max. 30 textures may be used
2Textured (2700+) - "The textures may be used freely in commercial or personal works but reselling or redistributing of the textures on other texture sites is forbidden"
textures.pedramk.com (~1000)
Freetextures.org (~1000)
Texturez (800+)
Free Texture Site (600+)
Back of Beyond (~500)
Zen Textures (450+)
Noctua Graphics (400+)
Texture King (300+)

Modelling

=> collada for exchange, tutorials, tutorials and links for normal map baking, tools