Here are links to files I've made specifically for UT2003 (thanks to SkinCity for letting me link to the site) and FilePlanet for the Ultim8 (2k3) link...
Phoenix [Artificial Lifeform] Skin (Released March 2004) - v1 [Final]
Ultim8 [Artificial Lifeform] Skin Pack (Released March 2004) - v1 [Final]
2Clones [Homo Sapiens] [Geneboosted] Skin Pack (Released February 2004) - v1 [Final]
Rogue [Human Male] Skin (Released February 2004) - v1 [Final]
Diesel [Human Male] Skin (Released January 2004) - v1 [Final]
Blood [Almost Human] Skin (Released January 2004) - v1 [Final]
Elite [Homo Sapiens] [Geneboosted] Skin (Released December 2003) - v1 [Final]
Hero [Human Male] Skin (Released December 2003) - v2 [Final]