Abstracts
Geometric images produced algorithmically within the Ultra Fractal software.
Works without obvious spiral structures. Many of these images do still feature self-similar shapes that appear at different scales throughout.
Iconic fractal art features structures from the classic Mandelbrot and Julia formulas. There's also a sub-gallery of Mandelbrot midgets herein.
Works that feature gnarled shapes: "to twist into a knotted or distorted form," according to one dictionary definition. Also "crabby, cantankarous"—which might refer more to the artist than the art.
Spirals and other structures from the Tent formula. These often feature hard edges, slices, and interrupted or truncated shapes.
In addition to Mandelbrot and Julia spirals, there are lots of other fractal formulas that produce distorted and other non-classical spiral structure.