Uh, uh, uh. That's the question I had to answer for my final exam in art. Well kids... (just kidding) The skull is a symbol from Vanitas. It's a movement from the 16th-17th century. It started in Europe. (Netherlands I think). Vanitas is latin and it means "emptiness". A quote from Wikipedia: "suddenness of death; smoke, watches, and hourglasses, which symbolize the brevity of life; and musical instruments, which symbolize brevity and the ephemeral nature of life."
I guess you know that there are books about his exhibitions. I got the one about Glorious Excess and I can tell you about it, cause that's all I am sure about. I do not want to just tell you some bullsh**. So what GE is mostly about is the glory and fame. You can see the famous "person" (he actually has no face, it's just a skeleton) whose life is all about his fame and money and it hasn't been shown through his point of view, but from the point of view of a 3rd person.
Mike uses his art to show is what has happened/is happening to the thing we call "culture". Both shows represent the life of the skeleton, the way up to being famous. The skull can be also seen as a warning, showing us that this behavior could be dangerous or on the other side, it maybe symbolizes a life without fear of death. There are those 4 pictures called "Four Seasons". They are representing Andy Warhol, Kurt Cobain, James Dean and John Lennon, who all died because of their fame/glory.
The decision to use a skeleton for the main character is of course strongly connected to Vanitas, but at mean time also with Rock, Anorexia, the "artistic lifestyle" of skull-and-crossbone.
I really have written 10 pages about this :/ if you want to know more, please feel free to ask me.
Thanks for answering, but I guess you didn't read my question properly or maybe I wasn't very clear about it. I wasn't asking about GLXS specifically, because obviously the skull in those paintings represents the celebrity character. I was talking Mike's other artworks, like I said, the 'skull' imagery has figured in quite a few of his paintings (other than GE). I wonder if there's a reason behind this. Of course, we can only speculate as to what those images meant to Mike, but what about in general, what do images of skulls and skeletons symbolize in paintings?
I did read your question and that's why I said "I got the one about Glorious Excess and I can tell you about it, cause that's all I am sure about. I do not want to just tell you some bullsh**."
He took it from vanitas. I guess it's like Ed Sheeran's paw print. If you know what I mean...
Oh, okay. No worries :) I knew about the connection to Vanitas, but I think that only applies to GE artworks.
Also in a lot of MTM and ATS songs, death is a theme.
Methinks Mike's thinking about death. Whether consciously or subconsciously I'm not sure, but it's definitely there.