I can wholeheartedly recommand Farya Faraji’s and The Skaldic Bard’s music, on youtube. Both making historically-themed music.
As for Sabaton, can’t wait to see what they’ll do in their next album. In their latest music video they teased the Romans, Vikings, the Black Prince, Joan of Arc, Vlad the Impaler and a samurai. A napoleonic soldier too but it’s outside of AOE2 (not that I’ll complain about a song about Napoleon hon hon hon 
)