A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Prismatic Geometric Pattern Background 2 No Black
Source GDJ
A pattern derived from repeating unit cells each derived from part of a fractal rendering in paint.net.
Source Firkin
A grid of squares with green colours. Since the colours are randomly distributed it is automatically seamless.
Source Firkin
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
If you need a green background for your blog/website, try this one. Remember that Green Striped Background is seamlessly tileable.
Source V. Hartikainen
Inspired by this, I came up with this pattern. Madness!
Source Atle Mo
The green fibers pattern will work very well in grayscale as well.
Source Matteo Di Capua
Prismatic Triangular Background Design Mark II 5
Source GDJ
A pattern formed from a squared tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i.
Source Firkin
Zerro CC tillable texture of stones photographed and made by me. CC0
Source Sojan Janso
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin