Added the below image and entry to the 19th Century Trombone History Timeline (first half). It is noteworthy because it appears to show both rear-facing and traditional trombones playing in the same ensemble. It also represents yet another rear-facing trombone image; these pictures turn up surprisingly often throughout the 19th century.
I also added the image to the Ophicleide History and Images post, which I continue to update from time to time.
c. 1830—Vienna, Austria: K.k. Österreichischer Militair Leichen-Conduct, lithograph no. 8 from a series edited by Michael Tretsentsky, shows a military band that includes trombones with both traditional and rear-facing bells (see below image–click image for larger version; public domain) (Pirker).