Phew, this took long. But it's worth it!
I'm gonna make a high resolution version of this for my soon-to-be-born niece to post on her wall as a painting.
I think Celestia's hair took the longest because I couldn't figure out what to do with it. I wanted it to transition into the sky somehow. I like how it all looks.
Also the contrast difference between my desktop computer and laptop annoys me.
Enjoy, fellow Bronies.