Riot, you messed up.
Ok, so I discovered this the other day when I was re-reading some lore for Piltover. I was looking at the 'Visions of Piltover', when I took a look at some of the other art, specifically this piece in the "Trade is the lifeblood of piltover" bit, titled City of Progress. So, I then took a look at the art for this little giblet of lore. The art is decent, though it looks like concept art, but what I was most interested in was a technique I spotted in the background; taking a photo of a good background for composition, and painting over it to make it fit with the rest of the painting. This is used by professional artists, and some even use 3D modeling to get a better read on the lighting of the paintings. All good, right? I was just interested in the technique.
Until I realized that there was a stock-photo watermark on the entire background. Specifically, a major portion of the mountain and buildings in the background, specifically on the left half. Zoom in, you can see a white swirl, the trade-specific x-patterning on stock photos, and text.
Really? I mean, it looks like concept art, sure, but if it's that unprofessional why put it on a spotlight in your website?
Riot, get real. Whichever artist did this shouldn't be fired, per se, but I'd recommend a stern... talking to.