Did some testing with Repper Pro tonight, and this gray mid-tone pattern came out.
Source Atle Mo
Embossed lines and squares with subtle highlights.
Source Alex Parker
Background formed from the iconic plastic construction bricks that gave me endless hours of fun when I was a lad.
Source Firkin
Prismatic Geometric Tessellation Pattern 3 No Background
Source GDJ
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
I guess this one is inspired by an office. A dark office.
Source Andrés Rigo.
A seamless pattern based on a square tile that can be retrieved in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Brushed aluminum, in a bright gray version. Lovely 2X as well.
Source Andre Schouten
Bright gray tones with a hint of some metal surface.
Source Hendrik Lammers
Love me some light mesh on a Monday. Sharp.
Source Wilmotte Bastien
The edges of all the red objects line up either vertically or horizontally, but it doesn't appear so. Made from a square tile that can be got by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
Coming in at 666x666px, this is an evil big pattern, but nice and soft at the same time.
Source Atle Mo
ZeroCC tileabel stone granite texture, edited from pixabay. CC0
Source Sojan Janso
Dark wooden pattern, given the subtle treatment. based on texture from Cloaks.
One more in the line of patterns inspired by Japanese/Asian styles. Smooth.
Source Kim Ruddock
Remixed from an image that was uploaded to Pixabay by Pixeline
Source Firkin
Retro Circles Background 5 No Black
Source GDJ
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
A light background pattern with diagonal stripes. Here's a simple light striped background for you.
Source V. Hartikainen
From a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Same as gray sand but lighter. A sandy pattern with small light dots, and some angled strokes.
Source Atle Mo
Colorful Floral Background 3 No Black
Source GDJ
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
From an image on opengameart.org shared by rubberduck.
Source Firkin