I was in your (almost) same position. I finished undergrad in Urban Studies this past May, have no work experience (none!), and had been at a comm-coll taking RN pre-req's for a few semesters (in addition to the undergrad classes at the university)....
I'm actually in a comm-coll RN program now, but not so happy with it. It's the top-ranked program in my state as far as NCLEX pass-rates go, but I find it's not exactly what I want to do, so I'm now applying to Yale's GEPN program for next year.
Enough rambling on my part... To answer your question, I asked 3 of my undergrad professors for rec letters. One was my major advisor, another was a prof in my major, and the third was my foreign language prof (only prof I had for 4 consecutive semesters). I also asked my clinical instructor from the RN program that I'm currently in, but that was my back-up letter, as she doesn't know me as well as my other professors...
I would think that the admissions people at the entry into MSN programs expect you to have references that aren't quite so relevant to nursing. I mean, they're entry-into programs, right? I would suggest choosing the professors who knew you the best and, of course, liked you.
If those happen to be professors from courses that aren't particularly relevant to nursing, maybe you can use your essay/personal statement to work in how you'll apply what you learned in those courses to your nursing career. (Your understanding of chem is a basic foundation of physiology and/or safe and competent drug practices, for example; or perhaps it's that psych broadened your awareness of the role that an idividual's stage of life plays in one's physical and emotional health...)
Anyway, you get my point. Any entry-into program is going to want to know that your professors, regardless of subject matter, found you motivated and intelligent and that you are capable of applying your background to the science and art of nursing.
I wish you much luck with your application process!