This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
Derived from an image that was uploaded to Pixabay by mdmelo.
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
More bright luxury. This is a bit larger than fancy deboss, and with a bit more noise.
Source Viszt Péter
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
All good things come in threes, so I give you the third in my little concrete wall series.
Source Atle Mo
Black brick wall pattern. Brick your site up!
Source Alex Parker
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
Wild Oliva or Oliva Wilde? Darker than the others, sort of a medium dark pattern.
Source Badhon Ebrahim
Fabric-ish patterns are close to my heart. French Stucco to the rescue.
Source Christopher Buecheler
Abstract Stars Geometric Pattern Prismatic No Background
Source GDJ
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
A seamless background pattern with a texture of wood planks. This wood background pattern has vertically arranged planks. You may try to rotate it 90°, to see how it will look like when the wood planks are arranged horizontally.
Source V. Hartikainen
An abstract web texture of a polished blue stone (or does it look more like ice).
Source V. Hartikainen
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
This background pattern looks like bamboo to me. Feel free to download it for your website (for your blog perhaps?).
Source V. Hartikainen
Psychedelic Geometric Background No Black
Source GDJ