Some images of British;
@ Nutty - Don't use 18th century redcoats to represent 19th century rifleman, that'd just look ******ed.... They should be musketmen? How do you figure? The British Army didn't go uniformwise from fighting Massecussetts minutemen in the 18th Century one second to suddenly fighting Boer farmers wearing Khaki (The Boer war started very last years of the 19th century for the uneducated). And the notion that the Brits were late to adopt rifles and kept using muskets is just plain wrong - the British Army were using Rifles like the Baker in large numbers during wartime operations at the same time that the pre-Civil War U.S. Armies were chasing Indians around the plains with Brown Bess'. Indeed, the Martini-Henry rifle was almost ubiquitous with the British Army of the 19th century.
If you're going to develop a Rifleman unit re-skin for the English civ at all, don't restrict yourself to some Revolutionary War-era imagery. This is after all, a Riflemen development thread, not a Musketmen development thread.
23rd Royal Welch Fusiliers, circa Crimean War 1860s.
2nd Warwickshires, Anglo-Zulu War 1879 (Note that the helmets were actually supposed to be white, but enlisted and NCOs as well as field grade officers often dyed them with tea to make them a khaki colour).
Napoleonic Wars (So the early 1800s), 33rd Foot
If you want the ease of simply porting over a decent English rifleman unit, I think you'll find the Rifleman unit with the black pith helmet used for Avain's QC for Civ4 (in fact a number of Civ4 mods use the same model) is quite accurate, notwithstanding the fact that that the time there was a number of different uniforms that the British used until they truly took steps to standardise uniforms (with the exception of certain accoutrements) in 1905.