Some notes on images: The diagram below shows how the Stargate Eggbeater scans images. It successively displays vertical slices of a 142-pixel-high file. The top and bottom edges of the image appear at the bottom of the hoop; the middle (“equatorial axis”) of the image is what appears at the top of the hoop. Mirroring an image in preprocessing is often effective: since both sides of the hoop pass by the viewer rapidly as it’s spinning, the effect of an assymetrical image can sometimes be jarring or seizure-inducing. This is just a rule of thumb though; asymmetrical images can be effective. A second general rule is that filling too much space is bad. Most of the best images leave a generous amount of black or dark pixels to give the eye a break.
Dan uses Vectorworks for creating his patterns (dan-*.png). Kevin used ContextFreeArt for generating cool recursive art (e.g. the “tree” and “spiral” images). The fractal explorer GNU XaoS was used for the “fract” images. (these are really effective on the hoop when the edge detection filter is used; it usually results in interesting line art.)