Here are some interesting photographs by Denis Ramos, as reported by The Phoblogarpher. He uses a 16-stop ND filter to get surrealistic looking images with silky smooth skies. The images speak for themselves. Check them out.
FYI – these filters can be very expensive. You may be able to substitute a welders mask glass, which can be under $10.00. It has a green color to it, but if you’re doing B&W, maybe that won’t matter.