Jet3D (Color keyed) Transparency images.
TUTORIAL: How to make specific areas appear invisible 
for sprites, and other uses.

PaintShop Pro
or
Photoshop

TUTORIAL: Converting 32 bit (TAG) alpha channel 
transparency images for use in Jet3D.
(I had a need to convert some Lithtech textures back to 
8bit color key transparency

Paintshop pro
 

Transparency Textures "In a nutshell" - Ken Deel

Game texture creation: 
How to tile an image seamlessly to be used in your game.
In this tutorial I take a shot of some charred wood, 
and prepare it to be used in our game seamlessly tiled.
- Ken Deel

• Creating Skies with Terragen

• Creating Seamless Textures With Truespace 
  and Paint Shop Pro 

Seamless tiled textures:  
Can't have enough of these ; ) - Author unknown 

Another SEAMLESS TEXTURE  tutorial- PSIONIC

Texture tutorial: Making a silk purse from a...
-or- Necessity is the Mother of invention. -By Ken Deel      
Sometimes you are looking for a texture and can't find or 
capture the right looking image.  This tutorial shows an example of 
how you can take from one image to make another you can use.

is tutorial shows how to use the T filter in Photoshop to create a seamless 

Free high quality Textures:

http://www.gentex3d.freeuk.com

http://www.freetextures.com

texture, then blend the joins out so it loops.