From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
From a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Prismatic Abstract Geometric Background 5 No Black
Source GDJ
From a drawing in 'At home', J. Sowerby, J. Crane and T. Frederick, 1881.
Source Firkin
This one is amazing, truly original. Go use it!
Source Viahorizon
Prismatic Curved Diamond Pattern 5 No Background
Source GDJ
Remixed from a JPG that was uploaded to Pixabay by susanlu4esm
Source Firkin
Paper pattern with small dust particles and 45-degree strokes.
Source Atle Mo
A bit strange this one, but nice at the same time.
Source Diogo Silva
Fix and cc0 to get the tile this is based on.
Source SliverKnight
Same classic 45-degree pattern, dark version.
Source Luke McDonald
A beautiful dark wood pattern, superbly tiled.
Source Omar Alvarado
You know I’m a sucker for these. Well-crafted paper pattern.
Source Mihaela Hinayon
Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
A seamless stone-like background for blogs or any other type of websites.
Source V. Hartikainen
This ladies and gentlemen, is texturetastic! Love it.
Source Adam Pickering
Colorful Floral Background No Black
Source GDJ
Prismatic Abstract Background Design
Source GDJ
You could get a bit dizzy from this one, but it might come in handy.
Source Dertig Media
If you’re sick of the fancy 3D, grunge and noisy patterns, take a look at this flat 2D brick wall.
Source Listvetra
Luxury pattern, looking like it came right out of Paris.
Source Daniel Beaton
A free light orange brown wallpaper with vertical stripes designed for use as a tiled background on websites. An yet another background pattern with vertical stripes.
Source V. Hartikainen
This is a remix of "blue wave-seigaiha".I hope this subtle color version of Seigaiha would be suitable for background .
Source Yamachem
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin