Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
By popular request, an outline version of the pentagon pattern.
Source Atle Mo
Just what the name says, paper fibers. Always good to have.
Source Heliodor jalba
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Prismatic Polka Dots Mark II 2 No Background
Source GDJ
This was formed by distorting an image of a background on Pixabay.
Source Firkin
This is the remix of "polka dot seamless pattern".The image depicts polka dot seamless pattern.
Source Yamachem
A huge one at 800x600px. Made from a photo I took going home after work.
Source Atle Mo
A seamless pattern the starting point for which was a 'colour modulo' texture in Paint.net.
Source Firkin
Simple combination of stripy squares with their negatively coloured counterparts
Source Firkin
Used the 6th circle pattern designed by Viscious-Speed to create a print that can be used for card making or scrapbooking. Save as a PDF file for the best printing option.
Source Lovinglf
A bit simplified version. Although it could be edited out to be simpler. Anyway, this time the tiling is converted to a pattern fill -which is using clipping for the tile's edges.
Source Lazur URH
Prismatic Abstract Geometric Background 4 No Black
Source GDJ
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
Geometric triangles seem to be quite hot these days.
Source Pixeden
Psychedelic Geometric Background No Black
Source GDJ
More tactile goodness. This time in the form of some rough cloth.
Source Bartosz Kaszubowski