Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
Luxurious looking pattern (for a T-shirt maybe?) with a hint of green.
Source Simon Meek
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I. Version with black background.
Source Firkin
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
From a drawing in 'An Old Maid's Love. A Dutch tale told in English', Maarten Maartens, 1891.
Source Firkin
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
A pale yellow background pattern with vertical stripes. The stripes are partially faded. I think this background image turned out pretty well, especially those faded stripes.
Source V. Hartikainen
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Prismatic Hypnotic Pattern No Background
Source GDJ
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
This was submitted in a beige color, hence the name. Now it’s a gray paper pattern.
Source Konstantin Ivanov
A seamless green background texture. The image is distributed under a Creative Commons License (like all of the images here).
Source V. Hartikainen
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A seamless background pattern with a texture of wood planks. This wood background pattern has vertically arranged planks. You may try to rotate it 90°, to see how it will look like when the wood planks are arranged horizontally.
Source V. Hartikainen
Prismatic Basic Pattern 2 No Background
Source GDJ
Have you wondered about how it feels to be buried alive? Here is the pattern for it.
Source Hendrik Lammers
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
From a drawing in 'La Principauté de Liège et les Pays-Bas au XVIe siècle', Société des Bibliophiles Liégeois ,1887.
Source Firkin