Oh, I always forget about their emblem, cuz it's not discussed in the books like Beauxbatons XD In my head it always looks like the Ferrari emblem because of the colours. I always did wonder how a tiny school like Durmstrang was able to accommodate Russia, Bulgaria, Norway, Sweden, Finland, Poland, Estonia, Latvia, Belarus, the Ukraine, Turkey, Czechoslovakia, Austria, Hungary, and Lithuania. Cuz I think Beauxbatons only sees students from western Europe like Spain, Italy, France, Belgium, Germany, the Netherlands, Greece, and Switzerland, despite having a large palace. Something about them just makes me think only European countries known for producing exceptional beauties attend Beauxbatons. Maybe it's the name of the school or just because of Fleur I think this.
True enough XD I figured you knew Durmstrang wasn't an all-boys school/Beaxubatons an all-girls, but at the same time, I wanted to clarify for anyone else reading my comment, since people tend to forget the movies are prone to getting things wrong. Not once in 13 years have I forgiven them for changing Ravenclaw's house colours and mascot, for instance.
'Course, we also never find out what happened to Durmstrang after the fall of He-Who-Must-Not-Be-Named. Slytherin became a lot less dark and more friendly, it seems. A lot less hostile. Though Anna and Elsa would be there long before even Grindlewald came into power so... moot point xD
They also work at Beauxbatons because, I think, of Fleur's descriptions of Beauxbatons at Chrismtastime. She mentions having ice sculptures that are "like 'uge statues of diamond" and a chorus of wood nymphs that serenade them. Their uniforms are also pale blue silk, so there's that. Goes with Elsa's dress.
Aesthetically, they definitely fit Beauxbatons, but geographically, they'd probably attend Durmstrang. I guess. XD But like I said, they could easily choice in to Beauxbatons.