There is so much amazing ASoIaF art, I swear it's impossible. What piece is your favorite? Also I couldn't just pick one, so I tried to pick one here and one there to show as much as I can... :D My all time favorite piece is that of Stark kids by aireenscolor, I mean, just look at those details!
I cannot NOT post at least something by Michael Komarck (bald Daenerys emerging from the pyre), ...
...Magali Villeneuve - the pact with the Children of the Forest...
...and Daenerys in Pentos, ...
...or Marc Simonetti - here is his depiction of the Wall, but he also coworked on that Pentos Dany above.
These three I personally consider the best ASoIaF artists, but you can try to prove me wrong... ;)
This Sansa one here I love for the idea, it is by PolliPo.
My favorite pic of Rhaegar and Lyanna (out of like millions out there) is probably this piece by FireEagleSpirit.
And I end my little collection here with an amazing imagination of Rhaego by S-Kinnaly.
And what are your favorites? :)