A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Prismatic Hypnotic Pattern No Background
Source GDJ
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
From a drawing in 'Artists and Arabs', Henry Blackburn, 1868
Source Firkin
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
The name alone is awesome, but so is this sweet dark pattern.
Source Federica Pelzel
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
Prismatic Curved Diamond Pattern 6 No Background
Source GDJ