A smooth mid-tone gray, or low contrast if you will, linen pattern.
Source Jordan Pittman
A background formed from an image of an old tile on the New York Metropolitan Museum of Art website. To get the base tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
No relation to the band, but damn it’s subtle!
Source Thomas Myrman
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Kaleidoscope Prismatic Abstract No Background
Source GDJ
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
Prismatic Abstract Geometric Background 5 No Black
Source GDJ
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless pattern drawn originally in Paint.net by distorting a slice of background pattern 116 and copying the resulting triangle numerous times.
Source Firkin
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
Prismatic Hexagonalism Pattern No Background
Source GDJ
From a drawing in 'Gately's World's Progress', Charles Beale, 1886.
Source Firkin
The tile can be had by using shift+alt+i on the selected rectangle in Inkscape
Source Firkin
Can never have too many knitting patterns, especially as nice as this.
Source Victoria Spahn
Prismatic Hexagonalist Pattern No Background
Source GDJ
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
One more updated pattern. Not really carbon fiber, but it’s the most popular pattern, so I’ll give you an extra choice.
Source Atle Mo
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic