A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
Same classic 45-degree pattern, dark version.
Source Luke McDonald
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
The following repeating website background is colored in a blue gray color and resembles a concrete wall or something similar to it.
Source V. Hartikainen
Fix and cc0 to get the tile this is based on.
Source SliverKnight
The starting point for this was a texture drawn with the 'Radial Colors' plug-in in Paint.net.
Source Firkin
Tiny circle waves, almost like the ocean.
Source Sagive
Pattern formed from simple shapes. Black version.
Source Firkin
Not sure if this is related to the Nami you get in Google image search, but hey, it’s nice!
Source Dertig Media
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
Clover with background for St. Patrick's Day. Add to a card with a doily, ribbon, a leprechaun or other embellishments.
Source BAJ
Bumps, highlight and shadows – all good things.
Source Badhon Ebrahim
A seamless pattern made from the gold Penrose triangle by GDJ and the two remixes
Source Firkin
New paper pattern with a slightly organic feel to it, using some thin threads.
Source Atle Mo
Remixed from a PNG that was uploaded to Pixabay by k_jprather
Source Firkin
A repeating background of beige paper with vintage look. Repeats to infinity, as usual.
Source V. Hartikainen
One more updated pattern. Not really carbon fiber, but it’s the most popular pattern, so I’ll give you an extra choice.
Source Atle Mo
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin