I just added 2 images and their captions to the Trombone History Timeline (17th century, 1626-1650 and 19th century, 1801-1825). Both are from Poland.

1649—Wladyslaw, Poland: The drawing, Orchestra of Wladyslaw IV Vasa, includes at least one trombone (see center-left of below drawing; public domain).

1804—Prószków, Poland: A pewter mounted Prószków faience jug features a trombonist who bears a strong resemblance to the trombonist in an anonymous Dutch etching from the 18th century (see second image, below). The pewter lid is monogrammed A.R.AE. and dated 1804 (see first image below; public domain; source: Lempertz Cologne auction 902 on 17 May 2007).