Dating research has repeatedly shown that in order to create romance, partners must have fun together, communicate positively with one another, and interact playfully. This cheap romantic idea fulfills all of these criteria, and will give you both something to giggle about for years to come.
To create romance with your partner in a unique and playful way, think like a child for a few minutes. Imagine what a preschooler would do if they were given some crayons and a bit of paint to make a gift for a loved one. Then, make your own loving piece of art in the same spirit, such as stick figures holding hands with hearts floating around them, or two handprints whose index fingers and thumbs make an upside down shaped heart. About.com's Guide to Child Parenting has some fantastic ideas and how-to's along these lines if you need other suggestions: Valentine's Crafts for Kids.
Once your masterpiece is finished, mail it to your partner with the words, “URGENT” written on the front in big red letters, and wait for them to say something about your efforts to create romance, even if the suspense kills you. If nothing else you'll get a laugh, and your partner will know you were thinking of them fondly.