Just gonna put this out there..the only reason I'm even checking out your artwork is because I was directed to a very...screwed up for lack of words series of screen shots on reddit....I'm not a huge MLP fan, I think it's cute, I watched it back in the 80's when I was like 4 years old...anyway I just had to see if this whole thing was real or not...I don't know whether to be scared or amused...anyway, cute art!
Don't you just hate it when people treat you like furniture? (And especially considering what happens after Pinkie Pie says, "I don't like being treated like I'm nothing!" Yeowch!)
Anyway, I love the styling job you've been using for the ponies, doing a great job of keeping them looking in-character while adding some more detail and personality to their works. The room's styling and use of darker tones, as is right for the period, looks great, and it's nice to see that Twilight can still stand out brightly even in those conditions due to the fire. It's a little odd that Pinkie looks more brunette to me, but whether that's by design (more sophisticated or mature) or an effect of the fire, it doesn't matter so much. She looks smart as a detective. (Note the careful word choice there.)
Now, why would Twilight put up with this debasement, especially when there's a perfectly good foreleg rest on that comfy chair? Or maybe Pinkie just wants to hold Twilight's bowler. The unicorn must have her reasons.
By the way, what made you decide to go with crystalline horns? I love the look but am surprised you don't mix it up more.
Also, lovely choice of books on the mantelpiece, plus the old-timey equivalent of the horse head busts seen all throughout Equestria.