My researches have so far turned up two things about the Aztecs:
1. The term "Aztec" is not very precise and may refer to various different groups depending on who's using it, and so is not necessarily the best term if you want to do a bunch of research on the subject. Since I don't know the best terms, yet, I'm going to stick with the general term.
2. I don't have the background/context to really understand a lot of the art. So your thoughts on them are probably as good as mine, if not better.
According to the Wikipedia, this is Xipe Totec, a fertility god associated with spring and patron of goldsmiths. He doesn't have four hands, though--he's wearing a flayed human skin. I'm not sure why the flayed person has spots. Maybe they were sick, or decorated like a jaguar? Or maybe spots just look nice.
Well, I assume this illustration from the Codex Fejérváry-Mayer is meant to illustrate the dangers of putting your foot into severed-head traps, but it's hard to say for sure. (The next two pictures are also from the Codex Fejérváry-Mayer.)
I have heard that it took anthropologists a long time to figure out that the Aztecs practiced human sacrifice. In retrospect, it seems kind of obvious.
This guy looks so bummed. And what are those snake-tail like things?