The post is fantastic, and the style is perfect for this sort of fan-art.
My one comment on the overall design is that I'm not sure how he's supposed to be sitting: his right leg seems oddly placed for his pose, as if it were resting up on a pile to his right, which would have to be uncomfortable given his posture. I know that in that pose it almost seems like he should have his legs cross or overlapped somehow.
That one criticism aside, this is delightful. I'd love to see you see if you can do a version that matches the League-style realism a bit more though -- the shading and lines on this definitely wouldn't fit an in-game splash. It's a beautiful piece though, and I'd definitely like that pose (with the leg/hip alignment issue tweaked a bit) in place of the current splash art for this skin.