Textures
If you decide to use these textures, don't hesitate to contact me with some screenshots. I love seeing my work being put to good use.
TRaK5 Texture Set

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A set of approximately 50 futuristic textures in 5 colour variants. 512x resolution, includes normal and bump maps, and an incomplete set of specular maps. Under an MIT("X11") license.
Source files(PSD)
Some (untested) game-specific packs:
Nexuiz/Darkplaces Pack - Normalmaps from this pack should also work in Doom3/Quake4.
Sauerbraten Pack
TRaK4 Texture Set

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Approximately 60 industrial/grunge/urban textures at 512x resolution with normal, bump, and specular maps. MIT license.
Source files (psd)
Below are my older, lower res, and frankly quite mediocre texture sets. You've been warned ;)
All these sets are diffuse only, at mostly 256x resolution.
Babel Texture Set

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License: GPL/cc-by-sa
Filth Texture Set

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License is GPL/CC-by-sa. Used in Schism. Source files (psd)
TRaK2 Texture Set

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License: GPL/cc-by-sa. Textures in use / Source files (psd)
TRaK3 Texture Set

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License: GPL/cc-by-sa Source files (psd)
Note: All GPL texture packs are licensed as "GPLv2 or later". All CC-BY-SA packs are licensed as cc-by-sa 3.0.
If you wish to use any of my textures under a different/modified license, do not hesitate to contact me.
Please note that these textures cannot be distributed with Open Arena due to some misunderstandings between me and the main OpenArena developer. In other words: do not use these textures in an Open Arena map if you want your work included in the main release.