From an image on opengameart.org shared by rubberduck.
Source Firkin
Seamless Prismatic Quadrilateral Line Art Pattern No Background
Source GDJ
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Prismatic Geometric Pattern Background No Black
Source GDJ
If you’re sick of the fancy 3D, grunge and noisy patterns, take a look at this flat 2D brick wall.
Source Listvetra
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Light gray pattern with an almost wall tile-like appearance.
Source Markus Tinner
This is the third pattern called Dark Denim, but hey, we all love them!
Source Brandon Jacoby
A seamless green background texture. The image is distributed under a Creative Commons License (like all of the images here).
Source V. Hartikainen
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.
Source Firkin
Zero CC tileable cork floor, photographed and made by me. CC0
Source Sojan Janso
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
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
Zero CC tileable hard cover green book, scanned and made by me. CC0
Source Sojan Janso
Prismatic Floral Background No Black
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
Prismatic Hexagonalism Pattern No Background
Source GDJ
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
Here I have tried to create something that would look like maple wood. Not sure how well it's turned out, but at least it looks like wood.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 2 No Background
Source GDJ
From a drawing in 'Real Sailor-Songs', John Ashton, 1891.
Source Firkin
No, not the band but the pattern. Simple squares in gray tones, of course.
Source Atle Mo
Thin lines, noise and texture creates this crisp dark denim pattern.
Source Marco Slooten