Some pieces of production artwork were shared a few months ago (which only really became known on the Discord server these past few hours) from backup CDs belonging to someone who worked on Jazz 3; included among this stuff is some scans of artwork Nick Stadler drew for Jazz 2, with files dated October/November 1996.

Since the originals no longer exist, this is the highest quality we'll ever see for most of these. (Unless Nick has higher-res scans elsewhere?)
Here's the lot of them on Imgur, 37 images total: https://imgur.com/a/9ScTl9Q

The highlights include: