A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
This one is rather fun and playful. The 2X could be used at 1X too!
Source Welsley
Here's a new paper-like background for free use on personal and commercial projects (this applies to all background patterns here).
Source V. Hartikainen
Colorful Floral Background 3 No Black
Source GDJ
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
Found on the ground in french cafe in kunming, Yunnan, china
Source Rejon
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Remixed from a drawing in 'Works. Popular edition', John Ruskin, 1886.
Source Firkin
Abstract Tiled Background Extended 11
Source GDJ
Prepared mostly as a raster in Paint.net and vectorised.
Source Firkin
The image depicts a seamless pattern of Japanese Edo pattern called "kikkou-matsu" or "亀甲松" meaning " tortoiseshell-pinetree".The real pinetree is like this: https://jp.pinterest.com/pin/500744052301065077/
Source Yamachem
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
Inspired by a drawing seen in 'City of Liverpool', James Picton, 1883.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
With a name this awesome, how can I go wrong?
Source Nikolay Boltachev
Nice little grid. Would work great as a base on top of some other patterns.
Source Arno Gregorian
The basic shapes never get old. Simple triangle pattern.
Source Atle Mo
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
People seem to enjoy dark patterns, so here is one with some circles.
Source Atle Mo
Abstract Tiled Background Extended 8
Source GDJ
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin