Well I mean the first thing that hinted to the image size being cropped. First difference at all I noticed was the red ribbon with the bell thing being totally different.
Riiiigghtt...
Anyway, Ahri seems to be the only example I can find where they just touched up the old image. There's a few times where they use the original image, but this only seems to happen with the inhuman champions, such as Fiddlesticks, or Anivia.
A lot of the time they're just redrawing old pictures, sometimes they're in new poses, sometimes they're in old poses. The art styles are all over the place, with sometimes very realistic styles, such as that third Mundo back there, and sometimes with rather anime-esque art styles. Sometimes the new artwork is awesome, but a lot of the time it's just redraws of the old artwork.
PAX Jax is a good example of the artist trying very hard to recreate what he/she sees.
Original:
Chinese:
You can see that everything's very similar, but none of it is quite the same.
I think in the case of Ahri, the artist just got lazy and decided to take the original image, recrop it, make a whole bunch of small changes to make it seem like it drawn by someone else, and just pass it off as their own work. Frankly if their work consists of making pointless copies of other people's works then I can't blame them for being lazy.
I just finished watching Legend of the Red Dragon/The New Legend of Shaolin. Something awesome happens in this movie about once every minute. A man walks across a bridge of thrown swords, an old lady throws darts so hard they hit enemies like bullets, the main villain travels around in a magic metal armadillo-like motorcycle thing, and so much more that I don't want to ruin.
I like the sound of this movie.