If not stated otherwise, the textures are licensed under the
CC Attribution 3.0 license (http://creativecommons.org/licenses/by/3.0/)

Author				  Work(s)
===============================================================================

Newton				- coal, earth, earth_dry, gold, ice3, ore,
					  rock, rocked_cracked, sand_rough, sulphur, tunnel, water, 
MimmoO				- ice2, brick
Nachtfalter			- acid, lava_red
Dustin Senos		- earth_rough
Andrew McConnochie	- granite
John Talbot			- snow1
					  source: http://www.flickr.com/photos/laserstars/2322517542/
					  license: CC-BY 2.0
Redwolf Design GmbH	- snow, lava