Hm, although I can't give a useful critique about this piece of art, I will say that you managed to capture each character's personality pretty well through their personal choice in glasses and body posture. The choice in background color fits each character's color design and/or personality nicely (various shades of purple and pink for Twilight, several cool but soft shades of green and blue for Rarity, etc.)
Oh, but maybe just a bit of Rarity's tail could have been drawn (I don't mean anything suggestive by saying this) between Pinke's legs. Then again, there would be little room for her tail hairs due to the obstruction of Fluttershy's mane (which otherwise looks pretty good, nice shading).
Overall, a nice job with (presumably) much hard work and effort involved~<3
Haha, this is a really original idea so kudos to you on that. I love how three out of the mane six have more practical glasses and the other three (that would be RD, Pinkie, and Rarity) went for more what works for them in terms of style.