Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
A white version of the very popular linen pattern.
Source Ant Ekşiler
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
Seamless Prismatic Quadrilateral Line Art Pattern No Background
Source GDJ
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
ZeroCC tileabel stone granite texture, edited from pixabay. CC0
Source Sojan Janso
Otis Ray Redding was an American soul singer-songwriter, record producer, arranger, and talent scout. So you know.
Source Thomas Myrman
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
It’s big, it’s gradient—and it’s square.
Source Brankic1979
Background formed from the original with an emboss effect.
Source Firkin
White fabric looking texture with some nice random wave features.
Source Hendrik Lammers
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
Prismatic Groovy Concentric Background 3
Source GDJ
A criss-cross pattern similar to one I saw mown into a sports field.
Source Firkin
If you don’t like cream and pixels, you’re in the wrong place.
Source Mizanur Rahman
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
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin