Hi, DoctorRad -
Welcome to Apple's Discussions.
They are in the same locations on either an original OS 9 Software Install CD that came with a machine or a retail OS 9 Install CD.
The original set of desktop pictures, patterns, etc., can be found in the Installation Tome, located here on the CD - (CD) >> Software Installers >> System Software >> Mac OS 9(.x.x) >> Installation Tome. You will need to use
TomeViewer in order to extract them from that Tome. TomeViewer runs in OS 9, maybe also in Classic, but not directly in OSX. Once you've accessed the Tome with TomeViewer, look for the items whose Type is JPEG.
How to use TomeViewer
Supplemental pictures, etc., can be found in the CD Extras folder on the CD. These are not in a Tome, and can just be copied off of the CD.
Although those files carry the Creator Code for the OS 9 Appearance control panel, they are in fact JPEG files (just tested one with GraphicConverter), so should be usable in OSX.