Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
Traced from a drawing in 'Household Stories from the Collection of the Brothers Grimm', Wilhelm Carl Grimm , 1882.
Source Firkin
I scanned a paper coffee cup. You know, in case you need it.
Source Atle Mo
Abstract Arbitrary Geometric Background derived from an image on Pixabay.
Source GDJ
Prismatic Hexagonalism Pattern No Background
Source GDJ
A seamless background colored in pale orange. It has a paper like texture with diagonal grid pattern.
Source V. Hartikainen
From a drawing in 'An Old Maid's Love. A Dutch tale told in English', Maarten Maartens, 1891.
Source Firkin
A seamless chequerboard pattern formed from a tile that can be had in Inkscape by selecting the rectangle and using shift+alt+i. Alternative colour scheme.
Source Firkin
A seamless pattern formed from cross 4. To get the original tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
An abstract texture of water. It's not perfect, but will do. You may download if you like it.
Source V. Hartikainen
Prismatic Isometric Cube Wireframe Pattern No Background
Source GDJ
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Tiny circle waves, almost like the ocean.
Source Sagive
This one takes you back to math class. Classic mathematic board underlay.
Source Josh Green
Embossed lines and squares with subtle highlights.
Source Alex Parker
A seamless pattern formed from a modified version of rwwgub's tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Element of beach pattern with background.
Source Rones