Mine were an even mix, perhaps leaning more to finished paintings. Looking back my folio seemed to be a mess of anything I thought they'd want to see, 3D, technical drawings, sketches, paintings. But yes, you're right in what you're saying, they're not asking for all of your pieces to be final, sketches and sketchbooks, unfinished stuff too, if they show a good example of the structure of the painting are really good. Have you done much figure work? Life drawing or otherwise? Oh and while I'm thinking about it, I don't know if you've done any big projects or anything, it may be good to bring along a small portion of your research and development and talk about the thought process behind a project.