Just drop the mainback.stp file into your series folder. I do have the default logos for the game shut off (deleted).
My PSD Template if you'd like to change cars to your favorite driver. https://www.mediafire.com/file/4f2l7wg7t9bgg1u/Mainback_Template.psd/file
You must use WinMip2 and convert BMP's to STP's to work in-game.