Custom Branded Ubuntu 22.04 ISO

I want to ship a polished, boot-ready Ubuntu 22.04 LTS image that carries my own branding and a small bundle of pre-installed apps (two or three in total; I will confirm the exact packages once the build process starts).

The image must:
• Display my custom wallpaper, GTK/Icons theme and a branded GRUB & splash screen from the very first boot.
• Come with the chosen applications fully configured so a user lands on the desktop ready to work—no additional downloads, PPAs or snaps required.
• Remain fully up-gradable through the standard Ubuntu repositories.

Deliverables
1. A tested, UEFI-compatible ISO (DVD/USB) that installs exactly as described.
2. The build script or documented steps (Cubict, Ubuntu Customizer, live-build, etc.) so I can reproduce the image later.
3. A short README outlining how you injected the wallpaper/theme, replaced boot artwork and embedded the apps.

If you already have experience with Cubic, live-build, or similar remastering tools, this should be straightforward. Clean, repeatable work is crucial, so please keep all modifications in version-controlled scripts where possible.