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
The classic 45-degree diagonal line pattern, done right.
Source Jorick van Hees
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
Prismatic Geometric Tessellation Pattern 2 No Background
Source GDJ
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
A dark brown fabric-like background texture with seamless pattern of winding stripes.
Source V. Hartikainen
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Formed by distorting a JPG from PublicDomainPictures
Source Firkin
An emulated “transparent” background pattern, like that of all kinds of computer graphics software.
Source AdamStanislav
I know there is one here already, but this is sexy!
Source Gjermund Gustavsen
Detailed but still subtle and quite original. Lovely gray shades.
Source Kim Ruddock
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
A textured blue background pattern with vertical stripes.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Here is a new seamless wood texture for using as blog or website backgrounds.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A light brushed aluminum pattern for your pleasure.
Source Tim Ward
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
A seamless pattern of leopard skin. It should look nice as a background element on web pages.
Source V. Hartikainen