Well, Yoda Power requested a Mameluk, so I'm going to try to do that first.
After that I'm going to do an Ancient era Camel Rider to replace the Horseman. It's based on a book I have, Warlords, and its a simple mounted warrior in a tunic with a small round shield and a spear.
In addition to the Mameluk, which is rather specific, I would like to do a somewhat more generic Middle Ages camel rider that looks somewhat like the Bedouin raiders Kal-El provided pictures for. It will probably have some sort of a lance.
For the Industrial Era, I was thinking about a sort of "Camelry" unit that basically is equipped with a rifle.
But if you, or anyone else, has any suggestions, I'll gladly take it into consideration. And provided I can find the props to do it with, I'll make it.