Those are hard. I would try a castle. I will look around and let you know if I find anything.
Look in the gallery under gothic and there is a medieval looking crown done by AZrunner. You might be able to use something like that.
This might give you some ideas:
http://caljavaonline.com/castles1.htm
If I were to do a medieval cake I would incorporate some kind of celtic ornament design. Depending on your skills there's all sorts of knotwork and circles and corners and what not - it can be made very religious or very non-religious, depending on what is needed. And it is so pretty.
Here is a site with wonderful Celtic wedding toppers,
http://www.celticart.com/castle.html
http://www.celticart.com/gallery.htm
Scroll to the one that says Philebeg
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