Hi there! I'm applying for Art Therapy this fall as well!
I can't speak yet as to how the interview process goes, but as for my resume, I definitely made it as detailed as possible. Since it was never specified that our resumes had to be brief, I included all my school, work and relevant experiences, as well as my awards and distinctions and art exhibitions (I'm an artist, my undergrad degree was in Painting). So you could say that I merged my professional and artistic resumes for my applications.