Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
CC0 remixed from a drawing. Walter Crane, 1914, Firkin.
Source SliverKnight
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Tile-able Dark Brown Wood Background. Feel free to use it as a background image in your designs or somewhere on the web. By the way, the color seems to be close to Coffee Brown.
Source V. Hartikainen
Alternative colour scheme for the original floral pattern.
Source Firkin
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A free background pattern with abstract green tiles.
Source V. Hartikainen
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
Subtle scratches on a light gray background.
Source Andrey Ovcharov
Light gray paper pattern with small traces of fiber and some dust.
Source Atle Mo
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Prismatic Groovy Concentric Background No Black
Source GDJ
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
This is the remix of an OCAL clipart called "Art Nouveau ornament" uploaded by "microcosme".Thanks.This is a seamless pattern of an Art Nouveau ornament.
Source Yamachem