I just came to think of a little list of Bands for you and also others. To some I have add also one or two special songs:
(In alphabetical order, not supposed to be complete of course^^)
Apocalyptica (Metal played by Cello, instrumental)
Blackmore' Night (the new band of Deep Purple's Richie Blackmore

)
Des Teufels Lockvögel (?)
Dunkelschön (?)
Eichenschild (?)
Elane (?)
Faun (?)
Gregorian (Gregorian Chant, but mostly modern songs)
Honigdieb (?)
In Extremo (doen't fit my taste but they fit the theme)
Letzte Instanz (Metal, they tried many things, even a bit new metal, but songs as "Sing Halleluhja", "Rapunzel" or "Der Geigenschüler" could fit great)
Nachtgeschrei (?)
Potentia Animi (?)
Qntal (Also very great medieval music, although they use some synthies, "Vos attestor" could be great for some fighting scene)
Saltatio Mortis (personnally I don't like them, but they could fit very good)
Sava (?)
Schandmaul (see Saltatio Mortis)
Schelmish (everything could fit)
Subway to Sally (the last two albums won't do, but the earlier the album is, the more it fits^^)
Tanzwut (this is, as they say, Medieval Industrial^^, most things do, rather powerful)
Thanateros (much influenced by Irish Folk)
Therion (Some Metal with classical influences)
Volkstrott (?)
Also some classical music could go (See John Williams and Indiana Jones or Star Wars)
(?) = I myself never listened to them
Hope this helps you and all others a bit.