Some rectangles, a bit of dust and grunge, plus a hint of concrete.
Source Atle Mo
White circles connecting on a light gray background.
Source Mark Collins
Prismatic Abstract Geometric Background 2
Source GDJ
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Here's a repeatable texture that resembles a light green concrete wall or something similar.
Source V. Hartikainen
A simple bump filter made upon request at irc #inkscape at freenode. Made a screen capture of the making here: https://youtu.be/TGAWYKVLxQw
Source Lazur URH
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
Black brick wall pattern. Brick your site up!
Source Alex Parker
A new one called white wall, not by me this time.
Source Yuji Honzawa
Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
A seamless pattern with a unit cell drawn as a bitmap in Paint.net and vectorized in Vector Magic.
Source Firkin
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
This pattern comes in orange, and it looks as if it is "made of glass".
Source V. Hartikainen
Light and tiny, just the way you like it.
Source Rohit Arun Rao
From a drawing in 'A Guide to the Guildhall of the City of London', John Baddeley, 1898.
Source Firkin
A seamless pattern formed from a square tile based on a jpg on Pixabay. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin