I don't know about battling knights specifically but I know for sure that I've seen some fabulous castle builds shared on here. Some with drawbridges etc. Kind of a slow time right now here on the forum. Apart from any responses with photos, I'd definitely suggest a search by Castle, Medieval and Knight.
I kind of have some preliminary things for a castle/knight setting like costumes which were bought after season and then there are 3 plaster-like faces that Grandinroad sold a few years back. I've seen them listed on eBay recently btw but a DIY face mold could also work to do something similar. The faces got me to thinking about a cemetery scene near a castle with the faces incorporated into the top of a stone sarcophagus for the dead "knights". Sort of like this....
As far as castle facades go here's a couple of amazing over-the-top inspirational medieval castle set ups:
First one by keithcorcoran and his wife in this thread for Maleficent:
http://www.halloweenforum.com/hallo...ent-castle-entrance-throne-garage-facade.html
Then there's the Boo Crew's medieval castle:
http://www.halloweenforum.com/hallo...medievalcastle-facade-home-haunted-house.html
I can't locate the castle with the drawbridge that I wanted to show you. Sure it's on here somewhere.
If you were fortunate to pick up the full size Skeleton Horse prop from Home Depot this past year, he'd make a great knight's horse. Really can't recall seeing any knight props that I can recall.