Ok, to be honest with you, the first thing that caught my attention was that the rabbit ears on the girl with darker hair (sorry I don't know your characters T.T they look interesting enough to get to know, though!) seem a bit awkward. I think it's because of the flat, straight on position and the simple shadows... The rest of the drawing has much depth & dimension - particularly the use of textures - but those ears feel...awkward. xD; Maybe if you used texture, or made the white a little darker...?

But aside from that, I really love how well this piece is composed. I like the play on symmetry and switched colors on the outfits... plus the graphical background is a very nice touch. <3 Need I even mention how gorgeous the dress designs are, too? Classy. Sweet job!