From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Psychedelic Geometric Background No Black
Source GDJ
Inspired by a pattern I saw in a 19th century book. This seamless pattern was created from a square tile. To get the tile, select the pattern in Inkscape and use shift+alt+i.
Source Firkin
Might not be super subtle, but quite original in its form.
Source Alex Smith
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
Tiny, tiny 3D cubes. Reminds me of the good old pattern from k10k.
Source Etienne Rallion
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
Zero CC tileable hard cover red book, scanned and made by me. CC0
Source Sojan Janso
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
From a drawing in 'Danmarks Riges Historie af J. Steenstrup, Kr. Erslev, A. Heise, V. Mollerup, J. A. Fridericia, E. Holm, A. D. Jørgensen', 1897.
Source Firkin
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
Clean and crisp lines all over the place. Wrap it up with this one.
Source Dax Kieran
So tiny, just 7 by 7 pixels – but still so sexy. Ah yes.
Source Dmitriy Prodchenko
A free seamless background image with a texture of dark red "canvas". It should look very nice on web sites.
Source V. Hartikainen
Seamless pattern formed from a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Prismatic Rounded Squares Grid 3 No Background
Source GDJ