Lovely pattern with some good-looking non-random noise lines.
Source Zucx
Tiny circle waves, almost like the ocean.
Source Sagive
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
A free black metallic background pattern. Here's a new pattern I made that looks metallic.
Source V. Hartikainen
The original has been presented as black on transparent and stored in the pattern definitions. To retrieve the unit tile select the rectangle in Inkscape and use shift+alt+i
Source Firkin
The classic notebook paper with horizontal stripes.
Source Are Sundnes
A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
A light background pattern with diagonal stripes. Here's a simple light striped background for you.
Source V. Hartikainen
A free seamless background image with a texture of dark red "canvas". It should look very nice on web sites.
Source V. Hartikainen
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
A heavy hitter at 400x400px, but lovely still.
Source Breezi
Derived from elements found in a floral ornament drawing on Pixabay.
Source Firkin
From a drawing in 'Heroes of North African Discovery', Nancy Meugens, 1894.
Source Firkin
This is a grid, only it’s noisy. You know. Reminds you of those printed grids you draw on.
Source Vectorpile
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ