Single Vanities: Above, in our photo from Wellborn, you will see two that are paired with a medium of drawers. Sometimes, they are designed with just one vanity (like in a hall bathroom). When you have space on both sides of the vanity instead of one going all the way across to both walls, this definitely gives the feeling of more space because THERE IS more space! I personally love this style.
Mirror: Also, using two small mirrors with decorative frames gives the appearance of more space and it adds an aesthetic value to the bathroom. It's that classy look that we so often design in many of our client's bathrooms these days, that I just love!
Vanities with Shelves: Also, you can have single vanities that have cabinets or you can have ones that have shelves (like above) which accentuate the spacious feel in a bathroom.
Neutral Paint: Don't go bold if you want your small bathroom to feel spacious. Dark colors definitely make one feel more closed in and smaller. Stick to lighter shades.
Do you have any design ideas to aid in the appearance of a small hall bath? Let me know in the comments!