The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Green Web Background, Seamless tile.
Source V. Hartikainen
A tile-able background for websites with paper-like texture and a grid pattern layered on top of it.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
This is a remix of "geometrical pattern 01".
Source Yamachem
A seamless pattern made from the gold Penrose triangle by GDJ and the two remixes
Source Firkin
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Light gray pattern with an almost wall tile-like appearance.
Source Markus Tinner
Zero CC tileable bark texture, photographed and made by me. CC0
Source Sojan Janso
Prismatic Curved Diamond Pattern 8 No Background
Source GDJ
I’m guessing this is related to the Sony Vaio? It’s a nice pattern no matter where it’s from.
Source Zigzain
Fix and cc0 to get the tile this is based on.
Source SliverKnight
Prismatic 3D Isometric Tessellation Pattern 6
Source GDJ
The image depicts a seamless pattern made using a bird's face.
Source Yamachem
Alternative colour scheme to the original.
Source Firkin
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
It’s like Shine Dotted’s sister, only rotated 45 degrees.
Source mediumidee
A seamless pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin