But he's not simply using them for visual reference. He's straight up tracing them. There's a big difference there.
The only thing that I might see as an issue is that these images aren't licensed to be free to use and I doubt he paid the owner's but there's enough variation between his finished drawings and the original photograph that it's a non-issue.That second example posted isn't a particularly strong argument, they're completely different. If you're saying he's plagiarizing those images, I think just the act of converting it from a photo to a drawing is enough to get away with it, even if he copied it exactly as shown. Plagiarism would be if he claimed these photos as his own or he traced another illustrator's work.
Again,
a lot more illustrators do this than just Greg Land. I think that they go to greater efforts to make sure their reference isn't as easily recognizable, using their own photographs for example, but they still trace.
I think this just shatters the romantic notion that people who aren't particularly knowledgeable about illustration have that an artist can just shut his eyes, picture a scene or subject in his head, and capture it perfectly on paper.
I remember reading the first issue of Fatale and I immediately recognized the reference Shawn Phillips used for a background, I was going to dig up the pictures but I found this forum thread, where I guess he posts at, where it was brought up:
http://www.606studios.com/bendisboard/showthread.php?213365-Fatale-(Brubaker)
I'm inclined to believe him that he didn't realize it was from Mad Men, the show is so popular he couldn't reasonably expect that no one would notice it. Still, he took an image from the internet that he doesn't own and traced it.
These days, a lot of comics illustrators straight up trace from Google Street View, 3D models and background scenes, and yes Google Image Search. You can call it lazy that they're not outside with their cameras and sketchbooks capturing these images themselves but it's a standard practice and pretty much every comics illustrators does it, some are just better at hiding it than Greg Land.