We added a primative to our ray tracer for a 3d slice of a 4d quaternion fractal. Below is such a slice.
Sadly, that doesn't show much of the 4d nature. Fortunately, during an earthquake we filmed a semi-reflective fractal in the graduate reading room as it slid though our dimension, allowing one to see consecutive 3d slices of the fractal. The footage is available here.
The "footage" was created with 284 separate pictures of the room for the backgrounds, in addition to pictures only used for calcuating the proper reflections. With perl scripts distributing the rendering across 12 machines, it took an hour to complete the movie.
One can render fractals much quicker if one doesn't mind making large approximations, or letting it look like the DVD player is hooked to the TV with telephone wire.