This seamless background image should look nice on websites. It has a dark blue gray texture with vertical stripes, it tiles seamlessly and, like all of the background images here, it's free. So, if you like it, take it!
Source V. Hartikainen
Carbon fiber is never out of fashion, so here is one more style for you.
Source Alfred Lee
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
A seamless dark leather-like background texture with diagonal lines that look like stitches.
Source V. Hartikainen
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Has nothing to do with toast, but it’s nice and subtle.
Source Pippin Lee
Light gray version of the Binding pattern that looks a bit like fabric.
Source Newbury
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Seamless Prismatic Pythagorean Line Art Pattern No Background. A seamless pattern that includes the original tile (go to Objects / Pattern / Pattern To Objects in Inkscape's menu to extract it).
Source GDJ
You know you love wood patterns, so here’s one more.
Source Richard Tabor
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
The act or state of corrugating or of being corrugated, a wrinkle; fold; furrow; ridge.
Source Anna Litvinuk
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Geometric lines are always hot, and this pattern is no exception.
Source Listvetra
Remixed from a drawing in 'Maidenhood; or, the Verge of the Stream', Laura Jewry, 1876.
Source Firkin
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Fabric-ish patterns are close to my heart. French Stucco to the rescue.
Source Christopher Buecheler
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
No idea what Nistri means, but it’s a crisp little pattern nonetheless.
Source Markus Reiter
Prismatic 3D Isometric Tessellation Pattern 6
Source GDJ
One can never have too few rice paper patterns, so here is one more.
Source Atle Mo
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i
Source Firkin