Here's an affordable air freshener we use in our very own bathroom. We've taken a small bowl from Target and filled it with scented bath salts from Kmart. We also added some vintage Avon fudgcicle-shaped hair combs that compliment our sweets-centric bathroom motif, but one could replace these with long candles, decorative branches, artificial flowers, or numerous other decorative items.
The initial strong scent of the salts dissipates quickly into a mild, but pleasant bouquet, and lasts for about a month. As the scent diminishes, simply shake salts to refresh, or simply pour them into your next bath!