Not sure if this is related to the Nami you get in Google image search, but hey, it’s nice!
Source Dertig Media
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
A free tileable background colored in off-white (antique white) color.
Source V. Hartikainen
Prismatic Hypnotic Pattern 2 No Background
Source GDJ
Tiny circle waves, almost like the ocean.
Source Sagive
The starting point for this was a texture drawn with the 'Radial Colors' plug-in in Paint.net.
Source Firkin
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
Prismatic Groovy Concentric Background
Source GDJ
A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Some dark 45 degree angles creating a nice pattern. Huge.
Source Dark Sharp Edges