The key to bathroom design for a small space is to give the illusion of size. This is achieved by maximising the circulation of light in the room and revealing as much floor space as possible.
Getting enough light in a room is always important but never more-so than in a bathroom. A dark bathroom can feel damp and cold to be in. Light can be maximised by use of reflective/gloss materials and light colours.
Even the best sanitary ware and layouts can be ruined with poorly chosen colours. Whether you want a vibrant, colourful room or a contemporary, muted colour palette its imperative that complimentary colours are used.