This could be a hippy vintage wallpaper.
Source Tileable Patterns
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
Looks a bit like concrete with subtle specks spread around the pattern.
Source Mladjan Antic
A monochrome pattern from a tile that can be had by selecting the rectangle in Inkscaope and using shift+alt+i
Source Firkin
CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Made by distorting a simple pattern using the 'sin waves' plugin for Paint.net and vectorising in Vector Magic
Source Firkin
A seamless pattern recreated from an image on Pixabay. It is reminiscent of parquet flooring and is formed from a square tile, which can be recovered in Inkscape by selecting the ungrouped rectangle and using shift-alt-I together.
Source Firkin
Everyone needs some stardust. Sprinkle it on your next project.
Source Atle Mo
I skipped number 3, because it wasn’t all that great. Sorry.
Source Dima Shiper
A blue background wallpaper for websites. It has a seamless texture with vertical stripes. It looks quite nice not only when using as a tiled background on websites, but also on computer desktops.
Source V. Hartikainen
This is a seamless pattern which is derived from a flower petal image.
Source Yamachem
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
Remixed from a drawing in 'A Child of the Age', Francis Adams, 1894.
Source Firkin
The rectangular tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
The basic shapes never get old. Simple triangle pattern.
Source Atle Mo
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Formed from a tile based on a drawing from 'Viaggi d'un artista nell'America Meridionale', Guido Boggiani, 1895.
Source Firkin
One more from Badhon, sharp horizontal lines making an embossed paper feeling.
Source Badhon Ebrahim
Love me some light mesh on a Monday. Sharp.
Source Wilmotte Bastien
Love the style on this one, very fresh. Diagonal diamond pattern. Get it?
Source INS
Utilising some flowers from Almeidah. To get the unit tile, select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
From a drawing in 'Les Chroniqueurs de l'Histoire de France depuis les origines jusqu'au XVIe siècle', Henriette Witt, 1884.
Source Firkin