From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Embossed lines and squares with subtle highlights.
Source Alex Parker
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless pattern based on a rectangular tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117
Source Viscious-Speed
A free seamless background pattern for use on websites.
Source V. Hartikainen
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Might not be super subtle, but quite original in its form.
Source Alex Smith
First pattern tailor-made for Retina, with many more to come. All the old ones are upscaled, in case you want to re-download.
Source Atle Mo
Seamless pattern inspired by a drawing on Pixabay. To get the tile this is formed from, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
And some more testing, this time with Seamless Studio. It’s Robots FFS!
Source Seamless Studio
Used a cherry by doctormo to make this seamless pattern
Source Firkin
This is the remix of "Colorful Floral Pattern Background 3" uploaded by "GDJ". Thanks.
Source Yamachem