It looks like a polished stone surface to me. Download it for free, as always.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
A lovely light gray pattern with stripes and a dash of noise.
Source V. Hartikainen
You guessed it – looks a bit like cloth.
Source Peax Webdesign
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
A very dark asfalt pattern based off of a photo taken with my iPhone.
Source Atle Mo
Here's a brown background pattern with subtle stripes. I hope you'll like the color. If not, feel free to change it using an image editor, if you know how of course. Personally, I'm using GIMP to create these backgrounds.
Source V. Hartikainen
It’s like Shine Dotted’s sister, only rotated 45 degrees.
Source mediumidee
Real snow that tiles, not easy. This is not perfect, but an attempt.
Source Atle Mo
Simple gray checkered lines, in light tones.
Source Radosław Rzepecki
This one is amazing, truly original. Go use it!
Source Viahorizon
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
A seamless green background texture. The image is distributed under a Creative Commons License (like all of the images here).
Source V. Hartikainen
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Zero CC tileable cork floor, photographed and made by me. CC0
Source Sojan Janso
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
Classic vertical lines, in all its subtlety.
Source Cody L
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin