The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
Another fairly simple design drawn in Paint.net and vectorized in Inkscape.
Source Firkin
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Prismatic Geometric Pattern Background 2
Source GDJ
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
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
A pattern drawn in Paint.net and vectorized in Vector Magic.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
An abstract Background pattern of purple twisty patterns.
Source TikiGiki
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
If you like it a bit trippy, this wave pattern might be for you.
Source Ian Soper
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight