With color, being truly a minimalist or going for a look that is minimal is key so when picking a design with two colors, for places that smaller it is recommended to pick white and a color such as bamboo green, light aqua, very soft green, real wood etc to go with the white. For just a bathroom that is on the larger scale, hues that are darker as with blacks, purples, reds, grays etc can be selected.
The bathroom may feel closed down in when working with patterns. However, for your bathrooms that is medium or large in size, the roof may be painted or one wall membrane may be decorated with designs in interior car paint or tiles with designs on them may be used. Addition of more patterns can bring about a design that is reflective of mid hundred years modern style.