In a small bathroom, less is always more. If you include a vanity, you will probably need to choose a very small unit. Depending on your needs, you can choose the style (cabinet or drawers or a combination) that is most suited to your needs. Recessed medicine cabinets (set into the wall, with an unframed mirror) are ideal in small bathrooms.
Organization is very important in a small bathroom. Creative use of nooks and crannies and recessing shelves and cabinets can conserve space, make the most of available space, and keep items close to where they will be used. There are many kinds of organizing units for drawers and for cabinets. If you are planning a custom vanity or shelves, you can insert whatever you wish in terms of dividers and such. There are different types of wall art that you can use to decorate various parts of your house. There are artworks painted on canvas and some that are printed on paper or fabric. Some are framed while others are not. Depending on your home design some may be more suitable than others.