This is sort of fresh, but still feels a bit old school.
Source Martuchox
A seamless pattern of dark bricks. Maybe it's not very realistic, but it looks good in my opinion.
Source V. Hartikainen
The image a seamless pattern derived from a weed which I can't identify.The original weed image is from here:https://jp.pinterest.com/pin/500744052301423641/
Source Yamachem
Small gradient crosses inside 45-degree boxes, or bigger crosses if you will.
Source Wassim
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
It’s okay to be square! A nice light gray pattern with random squares.
Source Waseem Dahman
Prismatic Hypnotic Pattern No Background
Source GDJ
The image depicts a seamless pattern of the design which includes a stylized lotus and a stylized crane.I referred to the original image in a book which is into public domain.
Source Yamachem
Not even 1kb, but very stylish. Gray thin lines.
Source Struck Axiom
This is the remix of an OCAL clipart called "Art Nouveau ornament" uploaded by "microcosme".Thanks.This is a seamless pattern of an Art Nouveau ornament.
Source Yamachem
A seamless pattern the unit cell for which can be had by selecting the rectangle in Inkscape and using shift+alt+i.
Source Firkin
From a drawing in 'Studies for Stories', Jean Ingelow, 1864.
Source Firkin
A slightly grainy paper pattern with small horizontal and vertical strokes.
Source Atle Mo
Abstract Tiled Background Extended 10
Source GDJ
A bit strange this one, but nice at the same time.
Source Diogo Silva
From a drawing in 'Cassell's Library of English Literature', Henry Morley, 1883.
Source Firkin
The tile this is formed from can be retrieved in Inkscape by selecting the rectangle and using shift+alt+i
Source Firkin
A seamless textured paper for backgrounds. Colored in pale orange hues.
Source V. Hartikainen