A dark wool background pattern with diagonal stripes #907
 Stripes  CC BY-SA 3.0

Feel free to download and use it, or see the rest of the dark background patterns that I have made. Anyway, I hope you will find something that you like.

Source V. Hartikainen

 More Textures
Pattern generator #161
 Noise  CC 0

A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.

Source Lazur URH

Prismatic Geometric Tessellation Pattern No Background@2X #552
 Noise  CC 0

Prismatic Geometric Tessellation Pattern No Background

Source GDJ

Prismatic Dots Background 4@2X #508
 Noise  CC 0

Prismatic Dots Background 4

Source GDJ

Floral pattern 7 (colour 5) #2287
 Green  CC 0

Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.

Source Firkin

Soft Kill@2X #319
 Dark  CC BY-SA 3.0

Pattern #100! A black classic knit-looking pattern.

Source Factorio.us Collective

Background pattern 66@2X #478
 Wall  CC 0

A background pattern drawn in Inkscape.

Source Firkin

Background pattern 328 (colour 6) #1796
 Red  CC 0

To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i

Source Firkin