You can add your own textures to the library of textures available to you in Dirty Pictures. At the top of the Options window, click on the Manage Texture Folders button. You can add a new folder full of textures to the library by clicking the Add button and selecting the folder that contains textures. Any tiff or jpeg files in the folder you select will be added to the library. You can also give the folder a nickname, which is a good idea if you have many texture sources. The folder’s name will be used as a default.
Dirty Pictures will prompt to generate preview files for the textures you add. It’s a good idea to go ahead and let Dirty Pictures make previews, because they are needed by the Texture Library window to display texture thumbnails. You can skip it now, but it will just make viewing slower later on.
You can also remove textures from the library if you wish by selecting the folder you wish to remove from the list and clicking the Remove button. The actual textures won’t be deleted from your disk, but you won’t be able to access them in Dirty Pictures unless you add it again later on.