The guest bedroom should have a cozy feel for your guests. You should decorate with minimal bedroom set. Not to bulky or dark. The darker the set the smaller it will make the room feel.

I would recommend white walls together with ivory trims or vice versa (actually ivory walls with white trim might be better).  I would recommend white or off-white draperies in a flowing fabric to give it a soft inviting look.  I would recommend blinds behind the draperies to be closed when you are not using the room.

Yellow pillows would be great; as would one or two vases with fresh yellow flowers, especially if you are expecting a guest.  In terms of color though the colors on the quilt and the pillows will help keep the eye focused on the focal point- the bed.

The closet should be modest in size. You shouldn't expect to keep anything in the closet. Maybe a small iron and board with a travel iron for your guests you use.