Anyone who happens to be wandering by the National Portrait Gallery, near Trafalgar Square, can go to Room 28 where a small portrait of JKJ by Solomon Joseph Solomon is currently on display. (It’s not especially attractive but it is the real thing. And both artist and sitter have a rather nice symmetry to their names!)
In total, the NPG holds 31 portraits of Jerome, 16 of which can be seen at this link:
http://www.npg.org.uk/collections/search/person/mp02421/jerome-klapka-jerome?search=sas&sText=jerome+k+jerome
(Left click on a portrait to see a larger version, and then left click on it again for even larger!)
In some of the photographs, other interesting people are also present, including Ottoline Morrell (No 10) and Virginia Woolf (No 12)