This is lovely, just the right amount of subtle noise, lines and textures.
Source Richard Tabor
Zero CC tileable grass texture, photographed and made by me. CC0
Source Sojan Janso
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
You know I’m a sucker for these. Well-crafted paper pattern.
Source Mihaela Hinayon
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Here's an yet another seamless note paper texture for use as a background on websites.
Source V. Hartikainen
Sometimes you just need the simplest thing.
Source Fabricio
The following repeating website background is colored in a blue gray color and resembles a concrete wall or something similar to it.
Source V. Hartikainen
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
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
A simple circle. That’s all it takes. This one is even transparent, for those who like that.
Source Saqib
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
A comeback for you: the popular Escheresque, now in black.
Source Patten
An abstract Background pattern of purple twisty patterns.
Source TikiGiki
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Zero CC tileable pine bark texture, photographed and made by me. CC0
Source Sojan Janso
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
White handmade paper pattern with small bumps.
Source Marquis