TO IMPORT INTO PSSG TEXTURE FILES USING THE RYDER PSSG EDITOR (CAPITAL LETTERS USED FOR EMPHASIS ONLY)
Always make a safe backup of files you're about to mod.
The 2 tga.DDS files in this folder need to be imported into each track's patchup_ot.pssg file (EXCEPT 4 MONACO & CLASSIC TRACKS), according to the graphical tutorial's screenshots provided inside the Graphical Tutorial folder (note that there also is another method, which is a faster one, if there is enough free disk space available: Open each circuit's patchup_ot.pssg into the Editor, Export All Files, copy the modded files in the new folder just created by the editor, click on Import All Files, save the new patchup_ot.pssg file, and delete the *_textures_pssg folder).
Off course, the always amazing Ryder PSSG Editor is required to import these two files into each circuit's patchup_ot.pssg file.
The link to the PSSG Editor (and other goodies) Download page is: http://petar.outer-heaven.net/downloads/
Special thanks and total appreciation to everybody involved in it's making, as well as in all the other tools.