I recently added the below images and captions to the Trombone History Timeline. In addition to the 3 rear-facing trombones and the buccin (dragon-bell trombone), low brass players may be interested in the 2 serpents and the ophicleide in these pictures. For more information, see the HubPages article Backward Advances: Rear-Facing Trombones Throughout History, and the blog post Serpent & Ophicleide: History and Images.
c. 1800—Germany: A print of military musicians entitled Turkische Musick der K. Baierischen Grendier Garde, now held in the German National Museum, includes a rear-facing trombone (see below detail; public domain).
c. 1800—Frankfurt am Main, Germany: Philipp Jakob Döring publishes a sheet of cut-outs of military musicians that includes a rear-facing trombone (see below detail; public domain) (German National Museum).
1800s—France: A print entitled Macédoines—Jongleurs—Tours de force et d’adresse features a row of musicians, including a dragon-bell trombone (see below detail; public domain) (Paris, Musée des Civilisations de l’Europe et de la Méditerranée).
1856-1900—The Netherlands: The publisher Glenisson and Sons publishes a print of military musicians that includes 2 rear-facing trombones (see below detail; public domain) (Catchpenny Prints of Royal Dutch Library).