I recall some rather awkward/amusing examples of this in media reports on certain video games. It's better now, but at one point, about half the featured images for articles about the game Super Mario World used some random pic from DeviantArt to represent the game (despite said art looking nothing like the original title), while a similar number of articles about Super Mario 64 represented it with a screenshot of the ROM hack Super Mario Star Road.

No-one knows exactly how said images ended up getting this sort of usage. Presumably some random journalist was on Google Images one day, come across pics that looked vaguely like what they remembered the games to look like, and just kinda went with it.

I also remember quite a few cases where fan-made box art mockups got accidentally used as the pictures of the real thing, and when the BBC used a logo from Halo to represent a real-life organisation.