There were 8 wallpapers that were officially given out on the official Tomb Raider 1 website. Thanks to old fansites 'Adventures Of Lara Croft' and 'Games Schtuff', we know what they are. They were based on the 8 renders that were released at the time, including credit screens, and were available in sizes 640 x 480 (256 colours), 800 x 600 (256 colours) and 800 x 600 (16m colours). The fansite AOLC also provided a bonus wallpaper that we see in Tomb Raider 1 promotions and merchandising.
These are 1024x768 - we've included slightly higher quality versions of the originals, but sadly we don't remember the original source.
This Japanese wallpaper came from Meagan Marie and Crystal Dynamics.