A topographic map like this has actually been requested a few times, so here you go!
Source Sam Feyaerts
A background pattern inspired by designs seen in 'Burghley. The Life of William Cecil', William Charlton, 1857.
Source Firkin
A heavy dark gray base, some subtle noise and a 45-degree grid makes this look like a pattern with a tactile feel to it.
Source Atle Mo
Dark wooden pattern, given the subtle treatment. based on texture from Cloaks.
A seamless pattern from a tile made from a jpg on Pixabay. To get the tile select the rectangle in Inkscape and use shift-alt-i.
Source Firkin
Prismatic Snowflakes Pattern 3 No Background
Source GDJ
Based on several public domain drawings on Wikimedia Commons. This was formed from a rectangular tile. The tile can be accessed in Inkscape by selecting the rectangle and using shift-alt-i
Source Firkin
This pack of filters can help you adding a blocky overlay to objects. May come handy at drawing blocks of stone.
Source Lazur URH
It has waves, so make sure you don’t get sea sickness.
Source CoolPatterns
A green background pattern with warped vertical stripes and a grunge look.
Source V. Hartikainen
8 by 8 pixels, and just what the title says.
Source pixilated
Actually, there's no clouds in it, but I think it looks quite nice.
Source V. Hartikainen
More Japanese-inspired patterns, Gold Scales this time.
Source Josh Green
Drawn in Paint.net using the kaleidoscope plug-in and vectorised.
Source Firkin
I took the liberty of using Dmitry’s pattern and made a version without perforation.
Source Atle Mo
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
To get the tile this is based on, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Some more diagonal lines and noise, because you know you want it.
Source Atle Mo
Not sure if this is related to the Nami you get in Google image search, but hey, it’s nice!
Source Dertig Media
This light yellow background pattern consists of an irregular pattern of spots. Here's a light background pattern with yellowish tint.
Source V. Hartikainen