Inigo Quilez   ::     ::  
These images were very famous in the 90s, like IFS and Popcorns images. In fact, "icons" are made by follow exactly the same procedures, just changing the equations. The nice thing is they tile quite well. In fact I used them for a 64 kilobyte realtime raytracing demo in 2002.

They were very popular in the 90s, the Fractint users might remember them. In fact I remember I copied some of the formulas from the "Symmetry in Chaos" book. Something like this:

k = λ + α⋅ |z| + β⋅R{zn}
z → k⋅ z + γ⋅conj(z) - ω⋅ z⋅ eiπ/2

The images below back in 2001 with that iteration formula. The way to get an image our of it it's the same as in ifs and popcorns.