In talking with the LintKing about what should be in Marius' room, tLK had a lot of good observations on what I was saying about Marius that I figured I ought to jot down for future reference.
[some paraphrasing required]
"The problem," I noted, "is that he's still in this transitional stage where he's suddenly free and clear of a guided destiny, without it seeming like he's free and clear of purpose, too. He's got the first opportunity to really focus on what he wants to know, but he can't deny the knowledge in what he's been trained."
"You're describing him as old-school, not really in Amber much, doesn't carry a lot, and that suggests that he doesn't have a lot of things. In fact, if he's old-school enough, he would perhaps have things in the room just to mislead people. Probably has gifts in there that people gave him that he didn't like, maybe something that's supposed to be sentimental. It's more as if the suite was a, 'I have to have it,' not a place where he lives. Think functional, think sparse."