My opinion (Hit or Miss, will make edits):
: Miss, she looks sort of ghostly, doesn't really capture the vixen nature about her. I'm no artist, but I think the splash would do better with a bit of a warmer palette (not warm, but warmer; I'd like some of the "charm" feel), larger/darker pupils (they look a bit too distant), and a hint of a smile (for the "charm" feel). Perhaps have her hair a bit neater, while still having that "wild" look (more on the side of curly than uneven lengths?). Maybe I'm off with the suggestions, I don't know...to me she looks like a scared fox running away, instead of a cunning fox luring you in closer... (I think Dynasty Ahri does a better job with Ahri's character)
: Such Hit, wow. Out of habit I found myself juking to the side irl to try to dodge the hook :P
: I'm a fan, Hit. Ezreal looks more like that cocky, punky kid he's supposed to be
: Miss; like you said, she looks too distant, also very elfish and too skinny, doesn't look like her lore depicts her as (which sounds like a retconn is coming....I hope they don't change too much...). Janna is supposed to be a human that becomes more otherworldly; her new splash makes her seem a bit too otherworldly, too inhuman (Frost Queen and Victorious Janna hit a better mark imo)
: Hit, my lord she looks awesome. Unsure, Legacy of Xion brings up some good points; I still like the splash, but wouldn't be opposed to some of the changes Legacy of Xion brings up. I agree with Ashes Arise, her thumbnail could use some touch ups (Lee Sin round 2/Shiny Diglett), but overall I like it.
: Miss, it looks like he's trying to be aggressive and playful at the same time, basically face pulling in opposite directions. Like Ashes Arise was saying, the cheeky expression is pretty canon. (See his old splash and Jade Dragon Wukong)
: Hit. Shen looks so awesome. I agree he looks a bit sinister, but he is a ninja; it'd be cool if they found a way to make that protector element a bit more apparent (for people who don't know what his ult does), but I like the new art.
: Hit. He actually looks like an assassin now. Poor helmet bro
: Hit, almost perfect, Not sure, actually, she looks a bit stylistically different than Rocket Jump Tristana, which is my personal favorite, but I do like the new look. I sort of wish her clothes looked a little less like she found them on the ground. Not sure what to suggest, I like the armor, but the clothes seem sort of plain in comparison.
: Hit, definite improvement, but not quite sure either, there's something sort of playful or comical about Veigar that doesn't fully come across. I do like the new look, though.
: Hit, he looks awesome
Basically, there's something playful about Ahri, Janna, and Wukong that I think the splashes don't capture; the art is great but it doesn't feel like the characters. There are certain characters that are very serious (Kayle, Shen, Talon), and the splashes do a good job with that, and there are characters that are more playful (Ezreal, Tristana) and their splashes do a good job with that too. I'd say Ahri's is the worse offender; I only really have a problem with Wukong/Janna's faces, they're almost there; the rest of the splash seems pretty good. Ahri's looks like it's a harrowing skin, which it really shouldn't, the layout and general look of the splash is good, just certain details and colors would make it much better imo
The ones I'm split about I generally like, but I don't know if they're as spot-on as the ones I listed as "Hits"