On one side of the cabinet is the storage space. On the other side, you have plenty of options. The most common ones are mirrors and hanging space.
A mirror is always a good option in a bathroom setting. However, if you already have a large vanity mirror, then this feature may become redundant.
A hanging space allows you to dry your towels and other wet items. It's a desirable feature as most bathrooms are lacking ample space for hanging.