Background Patterns - Citrone #248
 Fabric  CC BY-SA 3.0

If you want png files of this u can download them here : viscious-speed.deviantart.com/gallery/27635117

Source Viscious-Speed

 More Textures
Background pattern 269 #2062
 Dark  CC 0

A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i

Source Firkin

Batthern@2X #325
 Grid  CC BY-SA 3.0

Sometimes simple really is what you need, and this could fit you well.

Source Factorio.us Collective

45-Degree Fabric #1
 Fabric  CC BY-SA 3.0

Medium gray fabric pattern with 45-degree lines going across.

Source Atle Mo

Seamless Core Pattern #165
 Dark  CC 0

Seamless Core Pattern

Source GDJ

Background pattern 8 (greyscale) #210
 Dark  CC 0

Greyscale version of a pattern that came out of playing with the 'light rays' plug-in for Paint.net

Source Firkin

Prismatic Dots Background 6 #511
 Dark  CC 0

Prismatic Dots Background 6

Source GDJ

Background pattern 235 (colour 6) #2250
 Red  CC 0

To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.

Source Firkin

Tessellation 9 #2548
 Grid  CC 0

A seamless tessellation pattern. To get the tile this is formed from, select the pattern in Inkscape and use shift+alt+i.

Source Firkin

Bright Squares #87
 Light  CC BY-SA 3.0

It’s okay to be square! A nice light gray pattern with random squares.

Source Waseem Dahman

Ribbon pattern 2 (version 2, colour 5) #2035
 Colorful  CC 0

The tile this is based on can be retrieved by selecting the rectangle in Inkscape and using shift+alt+i.

Source Firkin

Tessellation 16 (colour 6) #2210
 Colorful  CC 0

The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i

Source Firkin

Art Nouveau ornament-seamless pattern #2550
 Brown  CC 0

This is the remix of an OCAL clipart called "Art Nouveau ornament" uploaded by "microcosme".Thanks.This is a seamless pattern of an Art Nouveau ornament.

Source Yamachem

Background pattern 227 (colour 4) #2311
 Green  CC 0

A seamless background drawn in Paint.net and vectorised with Vector Magic. The starting point was a photograph of drinking straws from Pixabay.

Source Firkin