As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background 2 No Black
Source GDJ
Formed by heavily distorting part of a an image of a fish uploaded to Pixabay by GLady
Source Firkin
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Hexagonal dark 3D pattern. What more can you ask for?
Source Norbert Levajsics
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Textured Red Brown Plastic, Free Background Pattern. Although there's already enough plastic in our lives, let's bring it to the web too.)
Source V. Hartikainen
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
Derived from a drawing in 'Historiske Afhandlinger', Adolf Jorgensen, 1898.
Source Firkin
Prismatic Snowflakes Pattern No Background
Source GDJ
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This seamless web background texture looks like gray stone. It's great for using as a background image on web pages, or on some of their elements. Anyway, I hope you will find use for it.
Source V. Hartikainen
Inspired by a drawing in 'Poems', James Smith, 1881.
Source Firkin
Bit of a strange name on this one, but still nice. Tiny gray square things.
Source Carlos Valdez
A pale olive green background with a seamless texture.
Source V. Hartikainen
Sweet and subtle white plaster with hints of noise and grunge.
Source Phil Maurer
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
Nicely crafted paper pattern, although a bit on the large side (500x593px).
Source Blaq Annabiosis
Remixed from a drawing in 'Some account of the Worshipful Company of Ironmongers', John Nicholl, 1866.
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
A playful triangle pattern with different shades of gray.
Source Dimitrie Hoekstra
Embossed lines and squares with subtle highlights.
Source Alex Parker
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady