This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Background formed from the original with an emboss effect.
Source Firkin
Remixed from a drawing in 'Line and form", Walter Crane, 1914.
Source Firkin
Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton
Prismatic Abstract Background Design No Black
Source GDJ
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
Pattern #100! A black classic knit-looking pattern.
Source Factorio.us Collective
From a drawing in 'Real Sailor-Songs', John Ashton, 1891.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
This could be a hippy vintage wallpaper.
Source Tileable Patterns
A pale orange background pattern with glossy groove stripes.
Source V. Hartikainen
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
The image is a remix of "edo pattern-samekomon".I changed the color of dots from black to white and added BG in light-brown.
Source Yamachem
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Psychedelic Geometric Background No Black
Source GDJ