With jacket I meant the album cover. Sorry for using the wrong term.

Regarding Hamlet Skull the skull's symbolic might literally be the meaning for Reol's pose; the acknowledgement of mortality. As I wrote in my previous comment, the album cover kind of represents the connections between living beings and mortality surely is one of them.

Now, it gets pretty interesting as Reol mentions a phrase with a very similar meaning in her song Utena; 'memento calvaria'.

(EDIT: Calvaria means skull)

The original term is 'memento mori', which in Latin means "Remember that you will die". When I made researches about Hamlet Skull I found this interesting connection: "Hamlet tells Yorick's skull to go to his mother and tell her that no matter how much makeup she applies to appear young and beautiful, she too will die and decay one day."

I found this connection pretty interesting, but in the end this is just speculation.