|Wow... astounding. You've already added some antialiasing I suppose, since the yellow balls look smooth.|
I was wondering how it'd all look if you changed slightly the direction of the ray when departing from the eye of the viewer, according to some noise function such as Perlin noise. It might add some "underwater currents" effect. Or this might be done when the ray is crossing through some cristaline material (within a ball f.i.), in order to simulate imperfections in the density of the material.