Pinned for the idea. Not sure how much I like the extension over the toilet. If were to do, vanity top should be one piece, with no cut line. Also: Consider how much the extra counter space would be needed.
start with special paper for charcoal soft and hard pencil, dry and oil pastels, marker pointer, pencils. Move to acrylic can be used with water. Water color and water color pencils. Oil paints and knife and finger techniques.