The image depicts a seamless pattern of a tortoise in tortoiseshell (hexagon).
Source Yamachem
Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
The name tells you it has curves. Oh yes, it does!
Source Peter Chon
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Because I love dark patterns, here is Brushed Alum in a dark coating.
Source Tim Ward
Simple wide squares with a small indent. Fits all.
Source Petr Šulc.
Classy golf-pants pattern, or crossed stripes if you will.
Source Will Monson
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Horizontal and vertical lines on a light gray background.
Source Adam Anlauf
A series of 5 patterns. That’s what the P stands for, if you didn’t guess it.
Source Dima Shiper
With a name like this, it has to be hot. Diagonal lines in light shades.
Source Isaac
The image depicts a seamless pattern which includes hexagonally-aligned gourds with BG in light-brown.
Source Yamachem
Clover with background for St. Patrick's Day. Add to a card with a doily, ribbon, a leprechaun or other embellishments.
Source BAJ
Prismatic Groovy Concentric Background 2 No Black
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
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Prismatic Isometric Cube Extra Pattern No Background
Source GDJ
Here's a subtle marble-like background for use on websites.
Source V. Hartikainen
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Fix and cc0 to get the tile this is based on.
Source SliverKnight
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
I love these crisp, tiny, super subtle patterns.
Source Badhon Ebrahim