A simple example on using clones. You can generate a nice base for a pattern fill quickly with it.
Source Lazur URH
Prismatic Polka Dots 3 No Background
Source GDJ
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift-alt-i.
Source Firkin
A seamless pattern created from a square tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
Zero CC tileable hard cover green book, scanned and made by me. CC0
Source Sojan Janso
Retro Circles Background 5 No Black
Source GDJ
Super dark, crisp and detailed. And a Kill Bill reference.
Source Badhon Ebrahim
The image depicts a seamless pattern of the design which includes a stylized lotus and a stylized crane.I referred to the original image in a book which is into public domain.
Source Yamachem
Vector version of a png that was uploaded to Pixabay by pencilparker
Source Firkin
Actually remixed from a pattern on Pixabay. But then noticed a very similar one on Openclipart.org uploaded by btj51q2.
Source Firkin
The unit cell for this seamless pattern can be had in Inkscape by selecting the rectangle and using shift+alt+i.
Source Firkin
I’m not going to lie – if you submit something with the words Norwegian and Rose in it, it’s likely I’ll publish it.
Source Fredrik Scheide
Sort of reminds me of those old house wallpapers.
Source Tish
A seamless pattern from a tile drawn in Paint.net and vectorised in Vector Magic
Source Firkin
Psychedelic Geometric Background No Black
Source GDJ
Here's a dark background pattern that contains a steel grid pattern as a texture. Use it as a website background or for other purposes. It's free!
Source V. Hartikainen
Derived from an image that was uploaded to Pixabay by Darkmoon1968
Source Firkin
This was formed by distorting an image of a background on Pixabay.
Source Firkin
Medium gray pattern with small strokes to give a weave effect.
Source Catherine
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Formed by distorting a JPG from PublicDomainPictures
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
This beige background pattern resembles a concrete wall with engravings or something similar to it.
Source V. Hartikainen