What historical rp would strike your interest ?
General Discussion
This is a really good question and nice discussion. It's interesting to see what appeals to people, especially the number of people who want to try something different (which provides an opportunity and a motivation to learn about aspects of history you didn't know before). I also very much agree with the people who were talking about the group nature of good rp -- Dio Kuhr always used to say that good rp is like improv theater carried out by an ensemble who all take turns sharing the spotlight.
Something else that I think is important is having a setting in which it is plausible and appropriate for different kinds of people to turn up and take part. The role-players you meet in SL are a diverse set of folks, from a lot of different backgrounds, locations, and viewpoints. It's part of what makes it an interesting environment. Everyone likes to play different kinds of historical characters: different nationalities, races, occupations, social classes and economic levels. This is one reason why I always liked Deadwood 1876 -- it was a gold rush town and historically it attracted a wide variety of people looking for good times or good fortune. You could be a skilled mexican blacksmith or an down-on-his-luck irish miner; a cranky old confederate widow or a whore with a heart of gold; a scalawag Yankee cardsharp or a well-born British tourist; and it all worked. One of the ancient Roman sims was like this too -- the city at the center of the empire drew all sorts of people of all classes and occupations. The interaction between them was often a lot of fun.
The other thing about having diversity of different classes and viewpoints is that you can have conflict as individuals and groups try to build a good life for themselves or maybe even run things. IC conflict helps generate a shared narrative and allows you to build and develop your character in interesting ways.
So what would I want to try personally? I have become somewhat attached to the 18th and early 19th centuries, and so, thinking about places that fit the bill with plausible diversity and potential for the good kind of conflict and drama, I would like to someday try New Orleans just after the Americans have taken over with the Louisiana Purchase. Or, I'd really like to try building a recreation of a settlement on the trans-Missippi frontier in the 1780s-90s, after the French settlements like Ste. Genevieve and St. Louis had been turned over to Spain (but before the Louisiana purchase), so there were a few Spanish soldiers and administrators, but the inhabitants were mostly French and French Canadians, both free and enslaved Africans, a wide range of people with mixed heritage, and even a few american and English trappers and traders, as well as Shawnee, Delaware and Osage Indians. A frontier environment by its nature can be pretty diverse even with people just passing through.