A handful of points... (speaking specifically of the second piece of art posted).
a) that is clearly not a leather gorget. It's a steel one. And it's huge. The wearer would not be able to raise his arms above his head to fight, and if the neck holee was so wide as to allow him to do so, raising his arms would blind him. One way or the other that things more likely to kill him than save his life.
b) as unrealistic depictions of armor goes, this one is not too bad. It's far too bulky, but it's less ridiculous looking than, for instance, the ridiculously oversized armor of World of Warcraft, Warhammer, or a few of the sillier illustrations in 4e. My original post was more a tweak at the idea that just because armor is all encompassing, it's somehow more realistic than loincloth clad barbarians or "chain mail bikinis". It's actually less. One could actually fight in a loin cloth or bikini; I defy anyone to do anything more than crash ridiculously into each other on horseback while wearing that hundred pound get up.
I'd rather go into combat with a boob window than all that metal.
c) while it doesn't apply to this particular illustration, armor is not the only thing most D&D art gets egregiously wrong. Everybody complains about the armor, but the depiction of weapons is generally even worse.
d) Where the heck are all these "chain mail bikinis" everybody keeps talking about? Thirty years ago they occasionally cropped up. But they were pretty thin on the ground even back in the 90's. Yet people act like this was a trend that was active up until last week.
As for the guitar pic. It looks fine to me. The guitar dates back to at least the 12th Century, most D&D technology is depicted as approximately 16th Century, and the Forgotten Realms has always had guitars (called 'yartings') in them. It looks like a finely crafted guitar. Awesome.