A bit like smudged paint or some sort of steel, here is scribble light.
Source Tegan Male
Cubes as far as your eyes can see. You know, because they tile.
Source Jan Meeus
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
Snap! It’s a pattern, and it’s not grayscale! Of course you can always change the color in Photoshop.
Source Atle Mo
Tweed is back in style – you heard it here first. Also, the @2X version here is great!
Source Simon Leo
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
Wasn't satisfied with the original's colouring. Too much component transfer and colormatrixes yet the results are lacking a bit. So this time it is a simple black to transparent fade, making it possible remixing easily once there will be other blending modes supported as well. Probably in inkscape 0.92.
Source Lazur URH
Remixed from a drawing in 'Очерки Русской Исторіи въ памятникахъ быта', Petr Polevoi, 1879.
Source Firkin
U.S.-based National Fire Protection Association standard fire diamond for flagging risks posed by hazardous materials. The red diamond has a number 0-4 depending on flammability. The blue diamond has a number 0-4 depending on health hazard. The yellow has a number 0-4 depending on reactivity. the white square has a special notice, e.g OX for oxidizer.
Source Firkin
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
Same classic 45-degree pattern, dark version.
Source Luke McDonald
A seamless pattern recreated from an image on Pixabay. It is reminiscent of parquet flooring and is formed from a square tile, which can be recovered in Inkscape by selecting the ungrouped rectangle and using shift-alt-I together.
Source Firkin
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
More in the paper realm, this time with fibers.
Source Jorge Fuentes
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Curved Diamond Pattern 7 No Background
Source GDJ
Prismatic Hexagonalism Pattern No Background
Source GDJ
Derived from a PNG that was uploaded to Pixabay by nutkitten
Source Firkin