These pictures are taken from The Making of The Dark Crystal: Creating a Unique Film by Christopher Finch. You can read it here on archive.org.
A grid of all the mystics.
a similar grid of all the Skeksis. they don't match up :/
Puppeteer Jean-Pierre Amiel manning one of the Mystic puppets.
The inside of a Skeksis head. (Notice the armature connecting the eyes!)
A two-person prototype of the Garthim rig, which didn't end up being used except for extreme closeups.
Producer Gary Kurtz talking to puppeteer Dave Goelz, who's puppeting this Skeksis!
A close up of the skekZok puppet to show the jewelry and costuming detail.
Most of the Skeksis robes were artificially aged with dirt, paint, and abrasive surfaces.
This appears to be someone helping a performer down (or up?) from the stilts used for the Landstriders.
A movie still of one of the Landstrider performers in action.
The set for the podling village during construction.
This picture shows how many people it could take to operate the Skeksis puppets. I count.. seven?
For the final scene of the movie, the Crystal Castle has to fall apart to reveal a castle of actual clear crystal beneath it.
This shows the crew's solution; a camera beneath a stucture rigged with precise explosives.