Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
Prismatic Rounded Squares Grid 4 No Background
Source GDJ
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
Zero CC tileable cork floor, photographed and made by me. CC0
Source Sojan Janso
Inspired by a 1930s wallpaper pattern I saw on TV.
Source Firkin
Background Wall, Art Abstract, Block Well & CC0 texture.
Source Ractapopulous
A subtle shadowed checkered pattern. Increase the lightness for even more subtle sexiness.
Source Josh Green
Turn your site into a dragon with this great scale pattern.
Source Alex Parker
Prismatic Snowflakes Pattern 3 No Background
Source GDJ
A seamlessly repeating background pattern of wood. The image is procedurally generated, and, I think, it's turned out quite well.
Source V. Hartikainen
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
After 1 comes 2, same but different. You get the idea.
Source Hendrik Lammers
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
ZeroCC tileable stone texture, edited from pixabay. CC0
Source Sojan Janso
A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
From a drawing in 'Resa i Afrika, genom Angola, Ovampo och Damaraland', P. Moller, 1899.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
Subtle scratches on a light gray background.
Source Andrey Ovcharov
Submitted by DomainsInfo – wtf, right? But hey, a free pattern.
Source DomainsInfo
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
The perfect pattern for all your blogs about type, or type-related matters.
Source Atle Mo