Blizzard allows textures to be replaced when the game loads by following some strict rules. The name of the folder structure and the aspect ratio of the files must be preserved.
This only happens once when you start the game. So after copying the textures you have to restart the game! (a realod is not sufficient).
This is the most efficient method of changing the textures if you care about every bit of CPU usage!


How to install: Copy the folder "RAIDFRAME" into the Interface folder of World of Warcraft. For most people this will be "C:\Program Files (x86)\World of Warcraft\_retail_\Interface".

How to tweak: I used Blpc (https://www.wowinterface.com/downloads/info18810-Blpc.html) to convert the default textures from .blp to .tga, which allows easy editing with software like GIMP: https://www.gimp.org/downloads/ (free and open source).

Things to consider: The name must NOT be changed. The aspect ratio of the texture must be preserved, so a 64 x 64 texture can be 128 x 128, but not 128 x 64. This is important! Color and texture can be changed to whatever you like!

