Didn't know horoscope ponies were Hasbro's idea... hmmm...
Anywho, lets start with the concept - the zodiac is usually affilated with ancient Greece, which makes the columns and the overall look of Virgo here quite befitting. Her walking on clouds (skipping the fact she's not a pegasus ) adds the feeling like we're visiting Mount Olympus, further playing on that aspect.
Of course, since zodiac is usually tied to ancient Greece, it makes this piece seem a bit "on the nose", bringing to mind various, mythology-related images from movies or paintings. As a whole, it stands unique, but the general feeling will always be familiar. That, in itself, is not necessary a bad thing, of course.
The technique is quite nicely chosen, playing homeage to the source material (MLP), bringing forth an even stronger feel of magic with the more lively colors as well as pushing forward that mythical vibe with its lighting. Each detail fits in perfectly with the rest, making this piece a solid whole.
The impact is also strong; most character presentations don't give out much (if any) emotions out their frames, yet you managed to take a different path with the pink glow spreading on the clouds, giving Virgo a form of majesty and grace. The carpet of clouds elevates her nicely, while the "weak", almost transparent name, written below her provides a very specific feeling to the recipant - that he already knows who this portrait represents, without the naming.
All in all it is one of the better pony portraits I've seen thus far... makes me kinda wonder how you'd handle Scorpio in that fashion... with the background beautifully filling the whole, in stead of being just plain, single-colored wall, like we were looking at some ID photo. A great example that from an even seemingly simple concept, one can make something stunning.
*Appears out of the smoke after a.... is not aware how long absent* Quite amazing It has such a heavenly feeling it's insane. Sooo homestuck didn't have any part in this particular selection of horoscope themes