Sometimes two dimensions is just not enough. Many calligraphers shy away from lettering on anything that is not paper, but I relish a challenge in this arena. I am happy to try new surfaces and like the variety this adds to my work. I have experimented over the years with what inks or paints or markers work on what surfaces.
I also got some great tips from the decorative painters group I was in for several years. Furniture is rarely cost effective for a client but quite rewarding to paint. Wood, pottery, metal, glass, plastic, rocks, fabric, children–if it will hold still, I will letter and paint on it.