Import all 24 themes' backgrounds from the main repo

Split per Nomarchy ROADMAP § Faster switches: wallpapers are runtime-only
data (94 MB, 97% of themes/) and now live here as a pinned non-flake
input, so a distro update stops re-copying them.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -1,2 +1,30 @@
 # Nomarchy-Wallpapers
 
+The default wallpapers for [Nomarchy](https://git.bemagri.xyz/bernardo/nomarchy)'s
+themes, split out of the main repo so that pulling a distro update stops
+paying ~94 MB for images that rarely change (Nomarchy's ROADMAP § Faster
+switches).
+
+## Layout
+
+```
+<theme-slug>/backgrounds/*.{png,jpg,jpeg,webp}
+```
+
+One directory per Nomarchy theme slug, mirroring what used to live at
+`themes/<slug>/backgrounds/` in the main repo. Nomarchy consumes this repo
+as a pinned **non-flake input** (`nomarchy-wallpapers`) and merges it with
+its in-repo theme data (palettes, previews, per-theme overrides) into the
+default themes root that `nomarchy-state-sync` reads.
+
+## Rules
+
+- Wallpapers are applied at **runtime only** (`swww` via
+  `nomarchy-state-sync`); nothing here is read at Nix eval.
+- Every theme in the main repo must have a non-empty directory here —
+  Nomarchy's `checks.theme-wholeswap` gates that, so **add the images here
+  and push before** adding a theme JSON there, then bump the
+  `nomarchy-wallpapers` input in the main repo's lock.
+- Downstream users never need this repo directly: custom wallpapers go in
+  their own flake checkout (`themes/<slug>/backgrounds/` there wins) or via
+  an explicit `wallpaper` path in `state.json`.