Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
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 the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 4
Source GDJ
A background pattern with blue on white vertical stripes.
Source V. Hartikainen
Element of beach pattern with background.
Source Rones
Zero CC tileable ground cracked, crackled, texture, made by me.
Source Sojan Janso
Similar to original, but without gaps in between the arrows. This seamless pattern was created from a rectangular tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Remixed from an image on Pixabay uploaded by Prawny
Source Firkin
I’m not going to use the word Retina for all the new patterns, but it just felt right for this one. Huge wood pattern for ya’ll.
Source Atle Mo
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
A comeback for you: the popular Escheresque, now in black.
Source Patten
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
Number five from the same submitter, makes my job easy.
Source Dima Shiper
Geometric triangles seem to be quite hot these days.
Source Pixeden
From a drawing in 'Hubert Montreuil, or the Huguenot and the Dragoon', Francisca Ouvry, 1873.
Source Firkin