The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A pattern formed from a photograph of a 16th century ceramic tile.
Source Firkin
Prismatic Groovy Concentric Background
Source GDJ
Geometric lines are always hot, and this pattern is no exception.
Source Listvetra
Sharp pixel pattern, just like the good old days.
Source Paridhi
The edges of all the red objects line up either vertically or horizontally, but it doesn't appear so. Made from a square tile that can be got by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
From a drawing in 'An Old Maid's Love. A Dutch tale told in English', Maarten Maartens, 1891.
Source Firkin
Adapted from an image that was uploaded to Pixabay by Anerma.
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A bit like some carbon, or knitted netting if you will.
Source Anna Litvinuk
Black & white version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net
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
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A seamless textured paper for backgrounds. Colored in pale orange hues.
Source V. Hartikainen
Pattern that came out of playing with the 'slinky' plug-in for Paint.net
Source Firkin
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
Thin lines, noise and texture creates this crisp dark denim pattern.
Source Marco Slooten
I guess this is inspired by the city of Ravenna in Italy and its stone walls.
Source Sentel