One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A bit of scratched up grayness. Always good.
Source Dmitry
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
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 seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
8 by 8 pixels, and just what the title says.
Source pixilated
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
Prismatic Abstract Line Art Pattern Background
Source GDJ
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
The image depicts meshed silhouettes of various things.The original image is an OCAL clipart called "Enter FOSSASIA 2016 #IoT T-shirt Design Contest" uploaded by "openclipart".Thanks.
Source Yamachem
From a drawing in 'Picturesque New Guinea', J Lindt, 1887.
Source Firkin
There are many carbon patterns, but this one is tiny.
Source Designova
You know I’m a sucker for these. Well-crafted paper pattern.
Source Mihaela Hinayon
Clean and crisp lines all over the place. Wrap it up with this one.
Source Dax Kieran
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
More bright luxury. This is a bit larger than fancy deboss, and with a bit more noise.
Source Viszt Péter