This was formed by distorting an image of a background on Pixabay.
Source Firkin
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
Prismatic Groovy Concentric Background 5 No Black
Source GDJ
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
Derived from an image that was uploaded to Pixabay by TheDigitalArtist
Source Firkin
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
Seamless Olive Green Web Background Image
Source V. Hartikainen
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i
Source Firkin
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
From a drawing in 'Danmarks Riges Historie af J. Steenstrup, Kr. Erslev, A. Heise, V. Mollerup, J. A. Fridericia, E. Holm, A. D. Jørgensen', 1897.
Source Firkin
Subtle scratches on a light gray background.
Source Andrey Ovcharov
The square tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
Remixed from a PNG that was uploaded to Pixabay by gingertea
Source Firkin