Coming in at 666x666px, this is an evil big pattern, but nice and soft at the same time.
Source Atle Mo
Prismatic Abstract Geometric Background 3
Source GDJ
Lovely light gray floral motif with some subtle shades.
Source GraphicsWall
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Adapted from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
A pattern drawn in Paint.net and vectorized in Inkscape.
Source Firkin
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
A seamless pattern the starting point for which was a 'light rays' rendering in Paint.net.
Source Firkin
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Retro Circles Background 7 No Black
Source GDJ
A seamless pattern based on a tile that can be achieved by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Sharp pixel pattern, just like the good old days.
Source Paridhi
Formed by distorting the inside front cover of 'Diversæ insectarum volatilium : icones ad vivum accuratissmè depictæ per celeberrimum pictorem', Jacob Hoefnagel, 1630.
Source Firkin
Zero CC tileable ground (#2) cracked, crackled texture, made by me. CC0
Source Sojan Janso
Prismatic Groovy Concentric Background No Black
Source GDJ
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
Not a pattern for fabrics, but one produced from a jpg of a stack of fabric items that was posted on Pixabay. The tile that this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin