Used a cherry by doctormo to make this seamless pattern
Source Firkin
From a design in 'Storia del Palazzo Vecchio in Firenze', Aurelio Gotti, 1889.
Source Firkin
Derived from a corner decoration itself found as a jpg on Pixabay.
Source Firkin
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
One more brick pattern. A bit more depth to this one.
Source Benjamin Ward
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
This is the remix of "Tileable Wave Pattern 2" uploaded by "Arvin61r58".Thanks.I added a wire-mesh fence seamless pattern as a lower layer.
Source Yamachem
A tile-able background for websites with paper-like texture and a grid pattern layered on top of it.
Source V. Hartikainen
A white version of the very popular linen pattern.
Source Ant Ekşiler
A seamless striped fabric-like texture colored in a dark reddish brown color.
Source V. Hartikainen
Prismatic Hexagonalist Pattern No Background
Source GDJ
Like the name suggests, this background image consists of a pattern of dark bricks. It may be an option for you, if you are looking for something that looks like a brick wall for use as a background on web pages. It's not a masterpiece, but looks pretty nice when is tiled.
Source V. Hartikainen
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
A bit of scratched up grayness. Always good.
Source Dmitry
Bigger is better, right? So here you have some large carbon fiber.
Source Factorio.us Collective
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward