Heavy depth and shadows here, but might work well on some mobile apps.
Source Damian Rivas
From a drawing in 'In an Enchanted Island', William Mallock, 1892.
Source Firkin
A seamless pattern formed from a square tile based on a jpg on Pixabay. The tile can be retrieved by selecting the rectangle in Inkscape and using shift-alt-I.
Source Firkin
Your eyes can trip a bit from looking at this – use it wisely.
Source Michal Chovanec
Not strictly seamless in that opposite edges are not identical. But they do marry up to make an interesting pattern
Source Firkin
Derived from an image that was uploaded to Pixabay by mdmelo.
Source Firkin
Adapted from a drawing in 'Line and form', Walter Crane, 1914.
Source Firkin
Prismatic Abstract Background Design No Black
Source GDJ
A beautiful dark padded pattern, like an old classic sofa.
Source Chris Baldie
From a drawing in 'Real Sailor-Songs', John Ashton, 1891.
Source Firkin
Seamless pattern formed from a tile that can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
From a drawing in 'Sun Pictures of the Norfolk Broads', Ernest Suffling, 1892.
Source Firkin
Remixed from a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Super simple but very nice indeed. Gray with vertical stripes.
Source Merrin Macleod
Same classic 45-degree pattern, dark version.
Source Luke McDonald
Everyone needs some stardust. Sprinkle it on your next project.
Source Atle Mo
Just to prove my point, here is a slightly modified dark version.
Source Atle Mo
The starting point for this was a texture drawn with the 'Radial Colors' plug-in in Paint.net.
Source Firkin
A free seamless background with pink spots.
Source V. Hartikainen
To get the tile this is based on select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
A background pattern with blue on white vertical stripes.
Source V. Hartikainen