A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
Prismatic Abstract Line Art Pattern Background 2
Source GDJ
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
From an image on opengameart.org shared by rubberduck.
Source Firkin
Mostly just mucked about with the colours and made one of the paths in the lead frame opaque. The glass remains transparent.
Source Firkin
So tiny, just 7 by 7 pixels – but still so sexy. Ah yes.
Source Dmitriy Prodchenko
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Just the symbols of the signs of the zodiac distributed in a chequer board-like pattern
Source Firkin
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
The starting point for this was a texture drawn with the 'Radial Colors' plug-in in Paint.net.
Source Firkin
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
This is a grid, only it’s noisy. You know. Reminds you of those printed grids you draw on.
Source Vectorpile
Sharp but soft triangles in light shades of gray.
Source Pixeden
A simple bump filter made upon request at irc #inkscape at freenode. Made a screen capture of the making here: https://youtu.be/TGAWYKVLxQw
Source Lazur URH
Classic 45-degree pattern, light version.
Source Luke McDonald
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
From an image on opengameart.org shared by rubberduck.
Source Firkin
A light background pattern with diagonal stripes. Here's a simple light striped background for you.
Source V. Hartikainen
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Love the style on this one, very fresh. Diagonal diamond pattern. Get it?
Source INS