Best Art: Liliana of the Veil
I love this piece! It's sexy, dark, and shows off Lili's power quite well. Another really nice thing about this piece is that you can see the full art on the card given that the text box is semi-transparent. Her dark dress, the flames in her hands, her piercing stare; Steve's portrayal of Liliana proves that she's not a chick to be messed with!
Worst Art: Everflowing Chalice
This art is still good, but I like it the least since I don't think it fits with what the card actually is. It's a chalice for sure (although it kind of looks like a candlestick) but it's not really overflowing per se. It's more glowing than anything else.
Blandest Art: Kranioceros
Art on cards is supposed to pop out and bring the card to life, but this one just sort of sits there (kind of like what this creature does). It's just... there. It's a beast that kind of looks displeased, like someone poked lightly with a blunt stick.
If you want to see more of Steve Argyle's work (something I highly recommend), check him out here. His art is definitely worth the peruse.