Sometimes simple really is what you need, and this could fit you well.
Source Factorio.us Collective
The image depicts polka dot seamless pattern.
Source Yamachem
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
A brown metallic grid pattern layered on top of a dark fabric texture. It should look great when using as a tiled background on web pages, especially blogs.
Source V. Hartikainen
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Prismatic Geometric Pattern Variation 2 With Background
Source GDJ
Colorful Floral Background No Black
Source GDJ
Remixed from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Prismatic Hexagonalism Pattern No Background
Source GDJ
Like the name says, light and gray, with some small dots and circles.
Source Brenda Lay
Number 4 in a series of 5 beautiful patterns. Can be found in colors on the submitter’s website.
Source Janos Koos
The starting point for this was drawn on the web site steamcoded.org/PolyskelionMaker.svg
Source Firkin
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Remixed from a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Detailed but still subtle and quite original. Lovely gray shades.
Source Kim Ruddock
Prismatic Polka Dots Mark II 2 No Background
Source GDJ
From a drawing in 'Cowdray: the history of a great English House', Julia Roundell, 1884.
Source Firkin
Design drawn in Paint.net, vectorised using Vector Magic and finished in Inkscape.
Source Firkin
You know you love wood patterns, so here’s one more.
Source Richard Tabor
This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
Zero CC tileable grass texture, photographed and made by me. CC0
Source Sojan Janso