I've used an oscillating stand fan on 3' of boxes to make an 8' tall head-turning witch. I left the fan blades and cage on it and draped black cloth over the front of it, hanging a witch mask on the front. The back of the fan was not covered to allow heat to escape and air to flow (somewhat). More black cloth was attached to the neck of the fan for the body, separate from the head cloth.
The fan blades also pushed air down the front of the prop and made the cloth move and billow slightly. At night, though the billowing was hardly noticable over the snake pit, strobe light, and me sneaking up on the ToT's.