The first pattern on here using opacity. Try it on a site with a colored background, or even using mixed colors.
Source Nathan Spady
Sort of like the Photoshop transparent background, but better!
Source Alex Parker
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
Prismatic Floral Pattern 3 Variation 3 No Background
Source GDJ
This is the remix of "Strawberry Pattern Background" uploaded by "GDJ". Thanks. I realigned strawberries so as to get seamless and changed the BG color.
Source Yamachem
Got some felt in my mailbox today, so I scanned it for you to use.
Source Atle Mo
A comeback for you: the popular Escheresque, now in black.
Source Patten
From a drawing in 'Prose and Verse ', William Linton, 1836.
Source Firkin
Three shades of gray makes this pattern look like a small carbon fiber surface. Great readability even for small fonts.
Source Atle Mo
Remixed from a drawing in 'Очерки Русской Исторіи въ памятникахъ быта', Petr Polevoi, 1879.
Source Firkin
A free seamless background pattern for use on websites.
Source V. Hartikainen
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
The tile this is based on can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Drawn in Paint.net and vectorised in Vector Magic.
Source Firkin
That’s what it is, a dark dot. Or sort of carbon looking.
Source Tsvetelin Nikolov
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Snowflakes Pattern No Background
Source GDJ
A fun-looking elastoplast/band-aid pattern. A hint of orange tone in this one.
Source Josh Green
Prismatic Groovy Concentric Background
Source GDJ
Here's a camo print with more tan and less green, such as might be used in a desert scenario. This is tileable, so it can be used as a wallpaper or background.
Source Eady
The basic shapes never get old. Simple triangle pattern.
Source Atle Mo