CC0 and a seamless pattern from a tile drawn in Paint.net .
Source SliverKnight
Remixed from a design on Pixabay. To get the tile this is based on select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
This pattern comes in orange, and it looks as if it is "made of glass".
Source V. Hartikainen
Prismatic Floral Pattern 3 Variation 3 No Background
Source GDJ
This one is quite simple in design, it consists of vertical stripes layered on top of a seamless texture.
Source V. Hartikainen
Zero CC tileable pine bark texture, photographed and made by me. CC0
Source Sojan Janso
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
A version without colours blended together to give a different look.
Source Firkin
A pattern derived from part of a fractal rendering in Paint.net.
Source Firkin
A dark metallic background with a pattern of stamped dots. Here's a dark "metallic" background pattern for you.
Source V. Hartikainen
Prismatic Curved Diamond Pattern 3 No Background
Source GDJ
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
A seamless pattern formed from cross 4. To get the original tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin