A braid from perlin noise, with careful lighting - both diffuse and from the energy accumulated by the thread as it weaves its way through the braid.

8 strong base palettes will give plenty of variation.

Straight P5, no GPU, it takes a while to render.
Single HTML file can be saved and run anywhere.

'd' to download when its finished. '2' to reload and double pixel density (most devices will give you 4000x4000 here)