It's easy to overlook the bathroom, because we spend very little time in there over the course of a day, and generally spend those times efficiently so that we can get back out into the world. Consider your bathroom as a private space, for guests or everyday use, and design from there.
The bathroom is an oasis, not only for grooming, but for self-indulgence and alone time. Whether in the bath or enjoying a home spa treatment, your bathroom should be inviting and calm. Is the light particularly lovely during a particular time of day? Give yourself the gift of decorating around that light. Does it steam up easily, or does water accumulate on the floor outside the shower? Decorate with durable and inexpensive rugs and furnishing.
For kids' bathrooms, of course, cleanliness is of the utmost importance. But a clean design aesthetic in the bathroom makes it welcoming and useful for everyone. Most of us tend to clutter the counters with products that gobble up space and never see use. Think of the sink area the way a chef thinks of his countertops! Only items that are useful, necessary, and preserves workspace are allowed.
If the idea of getting the curling iron or blow-dryer out from under the sink every day fatigues you, don't bother hiding them. Perhaps some industrial hooks or extra shelving with some inexpensive molding could clear up your clutter. Just think about the room's regular uses, and find a balance between simplicity and convenience that will suit your daily routine.