You could put nuts, cranberries, or peppermint candies in the vase and then nestle a candle in the middle. It would be for display purposes only. ;)
I love the idea of filling it with ornaments. I have 3 glass vases of different sizes filled with red/white/silver ornaments in my kitchen window sill and just love it!
You could fill it with pinecones and depending on the shape of the vase you could tie a red ribbon around the top for a little color.
You could fill it with some pretty holiday cookies. Some that are very pretty but not crumbly.
Depending on the vase shape, maybe you could put in a string of white lights?
Let me know what you end up doing! I have more vases and I'm always looking for new ideas, too!