A good starting point for a cardboard pattern. This would work well in a variety of colors.
Source Atle Mo
Same classic 45-degree pattern, dark version.
Source Luke McDonald
To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A black tile-able background with paper-like texture.
Source V. Hartikainen
Prismatic Basic Pattern 2 No Background
Source GDJ
Light honeycomb pattern made up of the classic hexagon shape.
Source Federica Pelzel
Number 5 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Remixed from a design seen in 'Burghley. The Life of William Cecil', William Charlton, 1857. The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A repeating graphic with ancient pattern. I came up with this name/title at last minute, so you may find that there is very little of ancientness in this pattern after all.
Source V. Hartikainen
From a drawing in 'Picturesque New Guinea', J Lindt, 1887.
Source Firkin
A bit of scratched up grayness. Always good.
Source Dmitry
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
A free seamless background with pink spots.
Source V. Hartikainen
This one is something special. I’d call it a flat pattern, too. Very well done, sir!
Source GetDiscount
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A version without colours blended together to give a different look.
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Prismatic Abstract Geometric Background 2 No Black
Source GDJ