A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.
Source Lazur URH
Prismatic Abstract Line Art Pattern Background
Source GDJ
A seamless pattern based on a tile that can be achieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
Remixed from a drawing in 'Hungary. A guide book. By several authors', 1890.
Source Firkin
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background No Black
Source GDJ
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
A simple but elegant classic. Every collection needs one of these.
Source Christopher Burton
Here's a new gray "fabric" pattern. Use it as backgrounds for websites or for other purposes.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 2 No Background
Source GDJ
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
"Beige Stone", Tileable Texture.
Source V. Hartikainen
Prismatic Polka Dots Mark II No Background
Source GDJ
A yellow tiled background... Blurriness, bokeh effect and rectangles pattern in one mix.
Source V. Hartikainen
This background pattern has futuristic look. So, maybe it could be used on websites or blogs dedicated to video games?!
Source V. Hartikainen
More Japanese-inspired patterns, Gold Scales this time.
Source Josh Green
Derived from an image that was uploaded to Pixabay by TheDigitalArtist
Source Firkin
A free seamless background texture that looks like a brown stone wall.
Source V. Hartikainen
More carbon fiber for your collections. This time in white or semi-dark gray.
Source Badhon Ebrahim
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
A seamless pattern the starting point for which was a 'light rays' rendering in Paint.net.
Source Firkin