Beginning in 1879, Koch worked with Friedrich von Thiersch, decorating the Alte Oper concert hall in Frankfurt am Main.

The first was in 1886, together with Alexander Kips [de], for the Jubilee Exhibition of the Prussian Academy of Arts, depicting the Temple of Zeus, in honor of the recent discovery of the Pergamon Altar, which was being brought to Berlin and reassembled.

Koch also decorated numerous public and private buildings with monumental historical scenes, which were very popular during the Imperial Prussia period.

At the beginning of the 20th century, Koch served as an expert witness in a prosecution test case brought against the publisher of Die Schönheit [de], who was accused by a civil keeper group (Volkswartbund) called the "Cologne Men's Association to Combat Public Immorality" (Kölner Männerverein zur Bekämpfung der öffentlicher Unsittlichkeit) of disseminating some photographic depictions of undesired nudity;[4] Die Schönheit (The Beauty) was a monthly journal for art and life, published between 1903 and 1914 in Berlin, Leipzig and Vienna, and again in Dresden from 1915 until 1932.

The Reich Court of Justice in Leipzig subsequently acquitted the journalist and publisher Karl Vanselow in two test cases in 1906 and 1909 with "the representation of naked people for the purpose of publicity for Freikörperkultur (free body culture) is declared for not punishable".