Using gimp and inkscape I’ve been playing with this design. its far from finished, but here are the steps I’ve taken so far:
Step 1: Take a picture. This is one of Kerry’s teapots. I liked the lighting but I should have taken this in front of a neutral background, which would have made the next step easier.
Step 2: Select the teapot. I zoomed in to 400% and used the free select tool. it takes a while tracing the teapot, but it gives better results than the scissors select tool. I also learned that you get better edges if you select feather edges (I moved the radius up to 22)

Step 3: Again in gimp, I desaturated the image (Colours – Desaturate) and then changed the threshold until I was getting a clear image. I inverted the colours and used the colour select tool to select the teapot and Ctrl-comma to change the colour.

Step 4: The teapot in gimp doesn’t have very smooth edges, so I opened the image in inkscape for this next step: Click on the image and then choose Path – trace bitmap. Then I could zoom in and use the edit path by nodes to smooth out the edges.