This could be a hippy vintage wallpaper.
Source Tileable Patterns
The edges of all the red objects line up either vertically or horizontally, but it doesn't appear so. Made from a square tile that can be got by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Might not be super subtle, but quite original in its form.
Source Alex Smith
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
From a drawing in 'Handbook of the excursions proposed to be made by the Lincoln Diocesan Architectural Society, on the 27th and 28th of May, 1857', Edward Trollope, 1857.
Source Firkin
Clean and crisp lines all over the place. Wrap it up with this one.
Source Dax Kieran
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
The tile this is based on was adapted from an image that was uploaded to Pixabay by frolicsomepl. It can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
CC0 remixed from a drawing. Walter Crane, 1914, Firkin.
Source SliverKnight
Pass parameters to the URL or edit the source code variables to configure the graph paper for the division desired.
Source JayNick
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Abstract Tiled Background Extended 10
Source GDJ
A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Pattern formed from simple shapes. Black version.
Source Firkin