LED Fan Display:

LED Fans are fan mechanisms lined with colour changing LED lights that enable the user to display an image or video. The fan spins the two LED lined arms to create the illusion of a floating image utilizing speed to hide the structure and allow for the image to appear as if it is existing on it’s own and unassisted.
3D Projection Pyramid:

The 3D Projection Pyramid is an easy to build and simple structure that consists of four plasic sides arranged to create a bottomless pyramid. This is then placed on top of a screen and a specially arranged video is played beneath. The screen reflects the video in the sides of the pyramid and creates the illusion that a 3D image exists inside.
BEST METHOD?
LED fans are limited by size and are costly whereas the Projection Pyramid can be made fairly cheaply and be scaled up to fit larger screens and therefore create larger 3D projections. So in terms of cost and use, I’d have to say that the Projection Pyramid seem like the best route to go down if I want to create larger Projections without spending all of my student loan on a small LED fan.
The downside to the Projection Pyramid is that you have this large structure over the projection but given I intend to display this in a dark space, hopefully the structure won’t be too noticeable or distracting from the work. There is also the issue of material and how it will stay up and what measurements I need to do to make it fit a larger screen.