jOeSmOe gives us a tutorial on advanced texturing using PhotoShop.
Texture Types Info
A definitive list of all worthy Sprites in HL
Improve the look of your maps using Valve's powerful 'Detail Texture' upgrade.
Decals are as easy as drawing in black & white and saving it into the right directory.
A small little tutorial on how to turn an object from a digital photo into a reasonable texture.
Using Terragen to render and put together a custom skybox.
HalfLife Crosshair Tutorial. From concept to reality.
PART 6 WATER Textures
using Wally and PhotoShop
PART 2 Masked Transparent textures
Learn how to incorporate your own custom textures into maps.
Part4 ANIMATED Textures
PART 5 TOGGLED AND TOGGLED ANIMATED TEXTURES
Create a Simple Spray with Transparency
Blast Marks using Painter
How to make animated sprites in Photoshop, and how to fix the frames of your sprites so they share the same palette.
How to make amazing metal textures like in Natural Selection
OK, this tutorial is about how to make a .wad. I'm only showing how to import a .bmp into a .wad with Wally
Changing the look of your HUD in Half-Life
Change the sound of your textures!
Relic explains the techniques on how to make textures that tile seamlessly.
TEXTURE REDUCTION TUTORIAL
Tutorial covering how to calculate the perfect texture rotations in hammer
This is NOT a tutorial on how to make textures. Instead, here are all the texture types I know of, the symbols their names should start with, roughly what they do, and some of the potential problems.
How to Make Transparent Textures with Wally
Half-Life Full Crosshair Tutorial.
Creating Textures for GoldSrc Mapping
The easiest way to make tileable textures with PhotoShop7 or above
Decals are images that you can 'spray-paint' on walls to...um make a statement. Making decals is extremely easy, so let's get to it.
PART1 SIMPLE TEXTURES AND WAD PACKING
Im no texture making expert, but ill give you what I believe to me the way to make textures and wads, wait keep reading!
Just as the title says, this tutorial will explain how to create a Splash Screen for your Mod.
The glass(es) texture(s)
PART3 ADDITIVE TRANSPARENT Textures
Texture dimensions have a significant effect on the appearance of the texture, the memory used by textures, and in a minor way on r_speeds.
So you want a movie to play, right before your Steam mod loads? Did you know that you can actually do it very simply with Steam?
The see through texture.
What are spraylogos? Spraylogos are images you can place on most surfaces multiplayer games, with the exception of models.
Making them, and getting them to work
Our first tutorial is creating a Simple spray