Here's a dark background pattern that contains a steel grid pattern as a texture. Use it as a website background or for other purposes. It's free!
Source V. Hartikainen
Background Wall, Art Abstract, Blue Well & CC0 texture.
Source Ractapopulous
Green Web Background, Seamless tile.
Source V. Hartikainen
Inspired by a drawing in 'Kulturgeschichte', Freidrich Hellwald, 1896.
Source Firkin
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Groovy Concentric Background No Black
Source GDJ
You just can’t get enough of the fabric patterns, so here is one more for your collection.
Source Krisp Designs
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
Colourful background achieved with gradient fills.
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
One more sharp little tile for you. Subtle circles this time.
Source Blunia
Colorful Floral Background 3 No Black
Source GDJ