I once had the idea to use space-filling curves to speed up CPU image convolutions by increasing the probability that 2D-adjacent pixels would be 1D-adjacent, and hopefully get loaded in the same cache line. IIRC the effect was measurable but not large enough to be worthwhile.
Aldo's project is awesome. I remember reading this a few years back and was really curious to see what would happen if you plotted color spaces other than RGB on a Hilbert Curve. Plotting colors in YIQ and HSV spaces turns out to be really fascinating.
There are several images of this sort on http://allrgb.com, which collects square images that have precisely one pixel of each of the 2^24 RGB colours.
