Here's the write-up from winteriscoming.net:
"A new photo points to Treme regular Michiel Huisman as the latest actor to join the cast of Game of Thrones.
A photo of the actor training hard was shared on Instagram yesterday by fitness pro Aaron Williamson, along with the comment , “1 more week w/ Michiel Huisman getting him ready to kick ass on Game of Thrones. Proud of this guy’s dedication; huge transformation from his Tremé days.”
The Dutch actor played Sonny, a musician struggling with drug and relationship problems on HBO’s Treme. An experienced singer and guitar player, he learned piano for his role on the show. Huisman also appeared in World War Z, BBC’s Margot, and in Black Book with Carice van Houten. He had an eight-episode arc as Liam McGuinnis last fall on ABC’s Nashville.
It’s unknown at this time what his role on Game of Thrones will be. We’ve reached out to HBO for an official confirmation of his casting."
I have to get ready for work, so I can't give much thought to whom he might play. Speculate away!