Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
Crossing lines with a subtle emboss effect on a dark background.
Source Stefan Aleksić
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
Remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
Luxurious looking pattern (for a T-shirt maybe?) with a hint of green.
Source Simon Meek
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
A seamless pattern drawn originally in Paint.net by distorting a slice of background pattern 116 and copying the resulting triangle numerous times.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The texture of this background image has some similarities with leather, and it's colored in a dark brown color. So, if you are looking for a dark brown background image for your website, this may be an option for you.
Source V. Hartikainen
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Sharp pixel pattern looking like some sort of fabric.
Source Dmitry
Dark blue concrete wall with some small dust spots.
Source Atle Mo
Colored maple leaves scattered on a surface. This is tileable, so it can be used as a background or wallpaper.
Source Eady
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
Prismatic Rounded Squares Grid 3 No Background
Source GDJ
One of the few full-color patterns here, but this one was just too good to pass up.
Source Alexey Usoltsev
Coming in at 666x666px, this is an evil big pattern, but nice and soft at the same time.
Source Atle Mo
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Prismatic Abstract Background Design No Black
Source GDJ
Never out of fashion and so much hotter than the 45º everyone knows, here is a sweet 60º line pattern.
Source Atle Mo
Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin