I just added the first image and caption below to the Trombone History Timeline (18th century). Although musical instruments are fairly common subjects in Baroque still life paintings, it is rare to find a trombone in one; they tend to dominate the image because of their length. However, below the first painting are two other Baroque still life paintings from the timeline that also include trombone.
c. 1725—France: A still life of musical instruments, attributed to Jean-Baptiste Oudry (1686-1755), includes what is probably a disassembled trombone (see below image; public domain) (source: europeana.eu, National Library of France).
c. 1670—Italy: Bartolomeo Bettera’s Still Life with Musical Instruments includes a trombone in the center of the image (see below image; public domain).
1663—Augsburg, Germany: Artist Franz Friedrich Franck (1627-1687) displays a trombone prominently in his painting, Musikstilleben (Music Still Life) (see below image; public domain).