Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
A seamless pattern formed from a square tile. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
Abstract Tiled Background Extended 12
Source GDJ
Dark pattern with some nice diagonal stitched lines crossing over.
Source Ashton
From a drawing in 'Navigations de Alouys de Cademoste.-La Navigation du Capitaine Pierre Sintre', Alvise da ca da Mosto, 1895.
Source Firkin
Submitted in a cream color, but you know how I like it.
Source Devin Holmes
Derived from an image that was uploaded to Pixabay by Kaz
Source Firkin
A seamless pattern formed from a sports car on clker.com. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Abstract Geometric Monochrome Pattern Prismatic No Background
Source GDJ
The image depicts a seamless pattern of a fishnet with a plenty of fish.It may be a lucky charm for fishermen.
Source Yamachem
This seamless web background texture looks like gray stone. It's great for using as a background image on web pages, or on some of their elements. Anyway, I hope you will find use for it.
Source V. Hartikainen
Might not be super subtle, but quite original in its form.
Source Alex Smith
Light square grid pattern, great for a “DIY projects” sort of website, maybe?
Source Rafael Almeida
Embossed lines and squares with subtle highlights.
Source Alex Parker
Very simple, very blu(e). Subtle and nice.
Source Seb Jachec
Prismatic Curved Diamond Pattern 2 No Background
Source GDJ
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
Classic vertical lines, in all its subtlety.
Source Cody L
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
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Pass parameters to the URL or edit the source code variables to configure the graph paper for the division desired.
Source JayNick
Looks as if it's spray painted on the wall. You can be sure that this pattern will seamlessly fill your backgrounds on web pages.
Source V. Hartikainen
Colour version of the original pattern inspired by the front cover of 'Old and New Paris', Henry Edwards, 1894.
Source Firkin