Trombone
I just added the below caption and image to the 17th century timeline (1st half). As you can see from this article, trombone was active in processions even well before this seemingly early example.
1614—Dresden, Germany: An image documenting a procession in honor of the baptism of Duke August depicts two trombones and a cornetto, followed by a person dressed as Mercury (see below image; public domain) (Dresden Staatsarchiv).
Just added the following two images and their captions to the 19th Century Timeline (first half and second half). The first one, Musique d’Amateurs, has also been added to the post Serpent & Ophicleide: History and Images. The second one, The Elections in England, will also be added to the article Backward Advances: Rear-Facing Trombones Throughout History.
1840—Epinal, France: An engraving entitled Musique d’Amateurs, published by Pellerin, features 3 trombones among 27 figures with various musical instruments. One of the trombones is a buccin, or dragon-bell instrument (see below image; click picture for larger version; public domain).
1852—Paris, France: A print by Janet-Lange entitled The Elections in England includes a rear-facing trombone (see detail below; public domain) (L’Illustration, July 17, 1852, p. 33).
I recently found the below image, which I will be adding to the Trombone History Timeline (19th century-first half). It is a print by a respected German artist, apparently produced in one of his more whimsical moments.
At 6’4″, I am often asked if you need to be tall to be a trombonist. The answer is of course not (many of my favorite trombonists are not particularly tall), but it doesn’t hurt.
c. 1840—A lithograph by respected German artist Heinrich Maria von Hess (1798-1863) portrays a short trombonist (see below image; public domain) (German National Museum, Nuremberg).
I just added two more images to the Trombone History Timeline (20th century). Both are military watercolors by Albert Escher (1833-1905), depicting soldiers of an earlier era. Notice that the trombone player is almost identical (including his instrument) in the two paintings, the differences being the uniforms and, of course, the facial hair.
c. 1901—A watercolor signed by Albert Escher (1833-1905) depicts a group of Dutch soldiers, including a military trombonist. The title is Netherlands, 1821 (see below image; public domain) (New York Public Library Digital Gallery).
c. 1901—A watercolor signed by Albert Escher (1833-1905) depicts a group of Italian soldiers, including a military trombonist. The title is Italy: Kingdom of the Two Sicilies, 1824-1828 (see below image; public domain) (New York Public Library Digital Gallery).
I just added the below image and caption to the Trombone History Timeline (17th century, first half). Another angel-trombone.
1638—Schleiz, Germany: A painting on the left organ shutter in the Bergkirche includes an angel trombonist among several angel musicians (see below image; public domain). 
I just added the following to the 19th century timeline (1st half) and to the post Serpent & Ophicleide: History and Images.
1833-1900—Turnhout, Belgium: A catchpenny print entitled Harmonie, probably published by Glenisson and Van Genechten, features musicians playing various instruments, including a buccin (trombone with dragon-head bell) and a standard trombone (see below detail; public domain) (Catchpenny Prints of the Dutch Royal Library).
I just added the following image and caption to 19th century timeline (1st half) and to the HubPages article, Backward Advances: Rear-Facing Trombones Throughout History.
1820-39—Rotterdam, Netherlands: A catchpenny print by T.C. Hoffers and A. van Alphen depicting various military instruments includes 2 rear-facing trombones, one with a dragon bell (see below detail; public domain) (Catchpenny Prints of the Dutch Royal Library).
I just added the below image and caption to the Trombone History Timeline (16th century).
1581—Dresden, Germany: A quartet of 3 strings and a trombone is depicted by artist Friedrich Bercht as part of celebrations surrounding the visit of Archduke Charles of Austria to Dresden (see below image; public domain) (Dresden, Sächsische Landesbibliothek).
I just added the below entry and image to the 19th century timeline (2nd half) and to the blog post, Serpent & Ophicleide: History and Images.
1865-1916—Netherlands: A painting by artist Willem Constantijn Staring (1847-1916) depicts bandsmen of the 9th Regiment Infantry, including a pair of trombonists and a musician playing a green-colored serpent (see below image; public domain).
Just added the below image and entry to the Trombone History Timeline (18th century). Interesting visual perspective—and definitely an unorthodox grip if it’s a trombone.
c. 1705—Irsee, Germany (near Kaufbeuren): A fresco by Magnus Remy (1674-1734) decorating the ceiling of Irsee Abbey features angels playing various brass instruments, including what appears to be a trombone (see below image; public domain).