A background pattern with blue on white vertical stripes.
Source V. Hartikainen
This is so subtle I hope you can see it! Tweak at will.
Source Alexandre Naud
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
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
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
Dare I call this a «flat pattern»? Probably not.
Source Dax Kieran
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Looks like an old rug or a computer chip.
Source Patutin Sergey
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
As the original image 's page size is too large for its image size, I remixed it.
Source Yamachem
This is so subtle you need to bring your magnifier!
Source Carlos Valdez
The image is a remix of "edo pattern-samekomon".I changed the color of dots from black to white and added BG in light-brown.
Source Yamachem
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Could be paper, could be a Polaroid frame – up to you!
Source Chaos
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Remixed from a drawing in 'Paul's Sister', Frances Peard, 1889.
Source Firkin
A seamless texture of worn out "cardboard".
Source V. Hartikainen
Derived from an image that was uploaded to Pixabay by starchim01
Source Firkin
From a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin