Alright! Forgive me if I post any you've already seen, but this is just gonna be a little compilation thingy.
So, I found
this one on the official forums.
This one as well, although it's a "through the ages" challenge - it does have two sections on medieval & Victorian simming, though.
This challenge is a royal legacy challenge that's apparently very historically accurate.
This is the original version of the challenge that you said you've already seen. Now,
this challenge is a *the* Royal Kingdom Challenge & it's be revised by it's original creator (& it's hosted here on MTS) so I figure I'd link it.
The next few challenges are a little off.
This one is actually an Egyptian-themed challenge but it deals with royalty so I'm sure it could be easily edited.
This challenge (Victorian) and
this challenge (medieval charter) are both hosted here on MTS but they're Sims 2 challenges. I don't know how easy they'd be the convert over to Sims 3, but, again, I just thought I'd suggest them.
I'm really sorry if I haven't suggested anything new! (Or if I've repeated anything - I tried to keep my tabs straight but I had a lot open.) If you still need more, let me know, but these are kinda what I've found so far.
Queen of the Land of Typos.