If you don't care about the technical stuff and already know what the demf/elmm/etc stuff means, just skip to the second spoiler tag.
First and foremost, the race, gender, and class that is associated with a texture can be determined by looking at the first four letters of the filename. The breakdown of these four letters will come down to either:
-demf [deatheater/man/fighter] (male warrior/guardian)
-demr [deatheater/man/ranger] (male hunter)
-dewf [deatheater/woman/fighter](female warrior/guardian)
-dewr [deatheater/woman/ranger] (female hunter)
-elmm [elf/man/mage] (male mage)
-elmr [elf/man/ranger] (male ranger/archer)
-elwm [elf/woman/mage] (female mage)
-elwr [elf/woman/ranger] (female ranger/archer)
-humf [human/man/fighter] (male fighter/defender)
-humm [human/man/mage] (male priest)
-huwf [human/woman/fighter] (female fighter/defender)
-huwm [human/woman/mage] (female priest)
-vimm [vail/man/mage] (male pagan/oracle)
-vimr [vail/man/ranger] (male assassin)
-viwm [vail/woman/mage] (female pagan/oracle)
-viwr [vail/woman/ranger] (female assassin)
When looking at armor, they are ordered as:
1. Boots (boot)
2. Gauntlets (hand)
3. Helmets (helmet)
4. Pants (lower)
5. Upper Armor (torso)
Keeping that in mind, the numbers at the end of the filename tell you which set the texture actually belongs to. According to my data.saf, it's something like this:
001 - "naked"
002 - Steel/Pelt/Toga/Copper/Cloth/Cotton
003 - Chain-Steel/Brutal/Blitz/Bronze/Leather/Dendron
004 - Scale/Hive/Metrin/Metal/Hard Leather/Quine
005 - Axo/Lusco/Hearth/Plate/Terra/Tathar
006 - Anga/Terron/Morcelle/Mirage/Unicorn/Loxe
007 - Legion/Ysilom/Serche/Sylma/Ebony/Willarin
008 - Mithril/Tatoram/Syron/Mithril/Freya/Sephiroth
009 - Adamas/Python/Hermit/Adamas/Dragon/Anor
010 - Ignota/Comination/Nascor/Vallum/Cleritas/Medicus
011 - Ferox/Deprimo/Scholar/Justia/Secor/Decoris
021 - ?
031 - ?
041 - Metal/Doublehide/BlackSap/BlueMetal/Spring/Sap
051 - (LEGENDARY) Axo/Lusco/Hearth/Plate/Terra/Tathar
052 - ?
061 - (LEGENDARY) Anga/Terron/Morcelle/Mirage/Unicorn/Loxe
062 - Fury/Greengol/Shaige/Jewel/Ive/Selva
071 - Suitroom/Trompe/Nevel/Porche/Portuba/Fiddess (LEGENDARY/GODDESS)Legion/Ysilom/Serche/Sylma/Ebony/Willarin
072 - (GODDESS) Mithril/Tatoram/Syron/Mithril/Freya/Sephiroth
081 - (LEGENDARY) Mithril/Tatoram/Syron/Mithril/Freya/Sephiroth
082 - (GODDESS) Adamas/Python/Hermit/Adamas/Dragon/Anor
091 - (LEGENDARY) Adamas/Python/Hermit/Adamas/Dragon/Anor
092 - Ohgerton/Teneran/Treffers/Daynorth/Raffinert/Ophiston
For example, elwm_lower0061 = Legendary Loxe Pants for female mages. So on and so forth...
If anyone can identify 21, 31, and 52 it'd be much appreciated - as of right now I can't tell what they are. Otherwise, there ya go.