This one is super crisp at 2X. Lined paper with some dust and scratches.
Source HQvectors
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
Prismatic Hexagonalist Pattern No Background
Source GDJ
Prismatic Hexagonalist Pattern No Background
Source GDJ
Sometimes you just need the simplest thing.
Source Fabricio
A seamless background pattern with impressed gray dots.
Source V. Hartikainen
Seamless Prismatic Quadrilateral Line Art Pattern No Background
Source GDJ
From a drawing in 'Jardyne's Wife', Charles Wills, 1891.
Source Firkin
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
Number 5 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
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
Honestly, who does not like a little pipe and mustache?
Source Luca Errico
This reminds me of Game Cube. A nice light 3D cube pattern.
Source Sander Ottens
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
Prismatic Groovy Concentric Background 2
Source GDJ
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
Derived from an image that was uploaded to Pixabay by darkmoon1968
Source Firkin