icarve,
I have to agree with Colin, though walnut is a beautiful wood it is harder to carve than many other good carving woods like pine, cedar, basswood, butternut, poplar/aspen, willow, or birch. My first woodspirit was in cottonwood bark and though it carves easily it has a tendency to break so might not be a good choice either.
If you do go with the walnut make sure your tools are RAZOR sharp!! Walnut, oak, and other HARD hardwoods can give you quite a workout on your honing and stropping skills.
Good whittlin, Cliff
Charles City, Iowa
http://cliffordparker.tripod.com