Some decorating tricks to make a small bathroom look bigger
You don't need to expand the surface of a bathroom to make better use of space and make it appear larger. Just keep the following ideas in mind (some of them are purely aesthetic; others require broader reform strategies):
1. Light it up well: install adequate lighting to eliminate shady corners. Create a false height effect by focusing low voltage indirect light towards the ceiling.
2. Reduce fixtures or replace them with smaller ones: replace the bathtub with a corner shower or remove a bulky vanity to put in its place an elegant pedestal sink.
3. Choose a more effective design: no more than two dominant horizontal lines. For example, the top of the wainscoting (wood covering up to a certain height from the wall) would mark a line and align the top of doors, windows, mirrors, etc .; would mark the second.
4. Eliminate physical and visual overload and avoid mixing a lot of materials: choose one such as tile for the floor and tile for the walls and countertop; use light-colored and small-scale wallpaper; avoid ruffled or embellished curtains and shaggy rugs; and get rid of junk.
5. Use mirrors: Large mirrors are deceiving and make small spaces appear much larger. In a bathroom, large mirrors can be used to make the walls look like windows.
Source: Five ways to make a small bathroom look bigger