Looks like a technical drawing board: small squares forming a nice grid.
Source We Are Pixel8
Inspired by a pattern I saw in a 19th century book. This seamless pattern was created from a square tile. To get the tile, select the pattern in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Geometric Tessellation Pattern No Background
Source GDJ
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
To get the tile this is made up from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Background formed from the original with an emboss effect
Source GDJ
Prismatic Snowflakes Pattern 3 No Background
Source GDJ
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
A bit like some carbon, or knitted netting if you will.
Source Anna Litvinuk
Used correctly, this could be nice. Used in a bad way, all hell will break loose.
Source Atle Mo
A light background pattern with diagonal stripes. Here's a simple light striped background for you.
Source V. Hartikainen
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
Not the most creative name, but it’s a good all-purpose light background.
Source Dmitry
Zero CC tileable moss or lichen covered stone texture, edited from pixabay. CC0
Source Sojan Janso
To get the tile this is based on, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Remixed from an image that was uploaded to Pixabay by CatherineClennan
Source Firkin
This is sort of fresh, but still feels a bit old school.
Source Martuchox
You don’t see many mid-tone patterns here, but this one is nice.
Source Joel Klein
A car pattern?! Can it be subtle? I say yes!
Source Radosław Rzepecki
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Prismatic Triangular Background Design Mark II 5
Source GDJ
With a name like this, it has to be hot. Diagonal lines in light shades.
Source Isaac
A seamless pattern formed from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A dark striped seamless pattern suitable for use as a background on websites.
Source V. Hartikainen
Retro Circles Background 5 No Black
Source GDJ