This was me eleven years ago at a midnight release party in San Francisco for Wrath of the Lich King. Blizzard had commissioned an ice carving of a literal Frozen Throne (and yes, it was cold, even with that seat cover they had).
I think your Death Star blowing up Alderaan analogy is correct. As people didn’t think Blizzard was promoting tyranny and genocide and personal violation by celebrating the throne Arthas sat on at this party. It is just people celebrating the video game they created.
Yes, it is dark humor of having a fire going under what’s supposed to be Teldrassil. But if you think about it hard enough, the humor is just as dark in the photo above for what Arthas did to Lordaeron and Quel’Thalas.