A repeating gloomy background image. This one consists of a pattern of black chains layered on top of a dark textured background.
Source V. Hartikainen
From a drawing in 'Art Embroidery', M.S. Lockwood and E. Glaister, 1878.
Source Firkin
Prismatic Abstract Geometric Background 2 No Black
Source GDJ
Remixed from a drawing in 'The March of Loyalty', Letitia MacClintock, 1884.
Source Firkin
From a drawing in 'Hyde Park from Domesday-Book to date', John Ashton, 1896.
Source Firkin
Zero CC tileable seed texture, edited by me to be seamless from a Pixabay image. CC0
Source Sojan Janso
Prismatic Groovy Concentric Background 3 No Black
Source GDJ
A comeback for you: the popular Escheresque, now in black.
Source Patten
Dark, crisp and subtle. Tiny black lines on top of some noise.
Source Wilmotte Bastien
Recreated from a pattern found in 'Az Osztrák-Magyar Monarchia irásban és képben', 1882. To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Basket Fibers, Basket Texture, Braid Background style CC0 texture.
Source 1A-Photoshop
Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
8 by 8 pixels, and just what the title says.
Source pixilated
A frame using leaves from an image that was uploaded to Pixabay by mayapujiati
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Remixed from a drawing in 'Chambéry à la fin du XIVe siècle', Timoleon Chapperon, 1863.
Source Firkin
A seamless pattern formed from a modified version of rwwgub's tile. To get the tile, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Heavily remixed from a drawing that was uploaded to Pixabay by ractapopulous
Source Firkin
Prismatic Floral Background No Black
Source GDJ
Dead simple but beautiful horizontal line pattern.
Source Fabian Schultz