Wall mounted cabinetry and appliances
This wall hung cabinet and sink combination from ThundaFunda to show how much open space you feel when there are NO legs on the floor.
Clear Shelving, Appliances and Accessories
Using clear glass or acrylic items eliminates visual obstructions to help make rooms look larger. (And curves are also supposed to make things look bigger.) This clear glass tub from Bathroom Accessories is one example.
This clear shower door from Natural Interior Design also expands the visual space.
And glass shelving units, like these featured at Apartment Therapy also do the trick!
White, Bright, Light
And above all else, keep it white, bright, and light in the bathroom with the use of light colors, reflective surfaces like tile and mirrors, and great lighting. This example is featured at Apartment Therapy.