The classic subtle pattern. Sort of wall/brick looking. Or moon-looking?
Source Joel Klein
Zero CC tileable Crackled Cement (streaks) texture, photographed and made by me. CC0
Source Sojan Janso
Embossed lines and squares with subtle highlights.
Source Alex Parker
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Retro Circles Background 8 No Black
Source GDJ
I scanned a paper coffee cup. You know, in case you need it.
Source Atle Mo
Prismatic Curved Diamond Pattern 2 No Background
Source GDJ
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Sharp diamond pattern. A small 24x18px tile.
Source Tom Neal
One more sharp little tile for you. Subtle circles this time.
Source Blunia
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
A free repetitive background with a dark concrete wall like texture. This one may be used in dark web site designs.
Source V. Hartikainen
Stefan is hard at work, this time with a funky pattern of squares.
Source Stefan Aleksić
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A seamless background of warped stripes on paper.
Source V. Hartikainen
A large (588x375px) sand-colored pattern for your ever-growing collection. Shrink at will.
Source Alex Tapein
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
This is the third pattern called Dark Denim, but hey, we all love them!
Source Brandon Jacoby
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous