To get the repeating unit, select the rectangle in Inkscape and use shift+alt+i
Source Firkin
A repeating background for websites with a texture of black groove stripes.
Source V. Hartikainen
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i
Source Firkin
A dark metal plate with an embossed grid pattern and a bit of rust. Here's a dark metal plate texture for use as a tiled background on web pages.
Source V. Hartikainen
Prismatic Abstract Background Design No Black
Source GDJ
This tiled background comes in red and consists of tiles that look like gemstones. It is more for blogs or social profiles, I think.
Source V. Hartikainen
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
The image depicts meshed silhouettes of various things.The original image is an OCAL clipart called "Enter FOSSASIA 2016 #IoT T-shirt Design Contest" uploaded by "openclipart".Thanks.
Source Yamachem
Prismatic Polyskelion Pattern No Background
Source GDJ
Background Wall, Art Abstract, Star Well & CC0 texture.
Source Ractapopulous
Nice and simple crossed lines in dark gray tones.
Source Stefan Aleksić
This could be a hippy vintage wallpaper.
Source Tileable Patterns
Pixel by pixel, sharp and clean. Very light pattern with clear lines.
Source M.Ashok
A new one called white wall, not by me this time.
Source Yuji Honzawa
Remixed from a JPG that was uploaded to Pixabay by theasad121
Source Firkin
Black And White Floral Pattern Background from PDP.
Source GDJ
Alternative colour scheme. Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin