Wallpaper
Wallpapers live in the same per-user directory most desktops use, and an SVG one recolors itself to the active color scheme before it's ever applied.
Open the picker from Super → Sobarch → Wallpaper. It lists every file in ~/.local/share/backgrounds/, the per-user counterpart of the /usr/share/backgrounds convention most distros ship their own default wallpapers under. Picking one applies it immediately to every connected monitor, scaled to cover.
SVG wallpapers recolor automatically
A plain raster image (JPG, PNG) is applied as-is. An SVG one can opt into recoloring by giving one element id="sobarch-bg" and another id="sobarch-accent", each with a plain fill="#RRGGBB" attribute. Those two get rewritten to the active scheme's base00/base0D before the file is ever shown, the same colors used across Hyprland, waybar, and everything else Theming covers. Sobarch's own shipped wallpaper (the default until you pick something else) follows this convention; drop your own SVG alongside it to get the same treatment.
The recolored SVG is rasterized to PNG before being handed to hyprpaper. hyprpaper's own raster scaling works correctly, but its SVG decoding doesn't render fills right, so an SVG is always converted first regardless of which app ends up displaying it.
When it re-applies
Nothing needs to be re-picked by hand: the current wallpaper is re-applied automatically whenever you switch color schemes (so an SVG wallpaper stays in sync with the rest of the desktop) and whenever the set of connected monitors changes, in addition to running once whenever you pick something new from the menu.