This is the contents of the 'Extras' folder that was included on the initial GD-ROM of Sonic Adventure for the Sega Dreamcast. The folder was only accessible when the GD-ROM was inserted into a disc drive on a PC or Macintosh from that era. The contents are Bitmap files that can be set as wallpaper or printed. It took a bit of work to get them from the original GD-ROM, to my old iBook, to my modern PC, to here, but here they are. Enjoy!