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
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
This one could be the shirt of a golf player. Angled lines in different thicknesses.
Source Olivier Pineda
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
This was formed by distorting an image of a background on Pixabay.
Source Firkin
From a drawing in 'An Old Maid's Love. A Dutch tale told in English', Maarten Maartens, 1891.
Source Firkin
The classic notebook paper with horizontal stripes.
Source Are Sundnes
Prismatic Polka Dots Mark II No Background
Source GDJ
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers
Zero CC Mossy stone tileable texture, photographed and made by me. CC0
Source Sojan Janso
An interesting dark spotted pattern at an angle.
Source Hendrik Lammers