This topic is just to have the how to's more accessible.
Early note, if you use any programs linked in this topic you do so on your own and we are not liable for any damages they may cause to your computer.
How to use custom textures (and models)
Create the following directories, they start from the game's root folder
Ex: C:\Ultima PSOBB\
Use the AFS Manager to extract the textures you want from ItemTex