Fix power menu bug and change default background image

Description of changes

Fixed Power Menu Bug
- The issue was caused by the command timing out before it finishes.
- Not certain why this is not an issue when mic is not in use.
Changed Default Ghaf Background Image

[x] Summary of the proposed changes in the PR description
[ ] More detailed description in the commit message(s)
[x] Commits are squashed into relevant entities - avoid a lot of minimal dev time commits in the PR
[x] Contribution guidelines followed
[ ] Ghaf documentation updated with the commit - https://tiiuae.github.io/ghaf/
[ ] PR linked to architecture documentation and requirement(s) (ticket id)
[x] Test procedure described (or includes tests). Select one or more:
- [x] Tested on Lenovo X1 x86_64
- [ ] Tested on Jetson Orin NX or AGX aarch64
- [ ] Tested on Polarfire riscv64
[ ] Author has run make-checks and it passes
[ ] All automatic Github Action checks pass - see actions
[x] Author has added reviewers and removed PR draft status
[ ] Change requires full re-installation
[x] Change can be updated with nixos-rebuild ... switch

[x] List all targets that this applies to: Lenovo X1
[ ] Is this a new feature
- [x] List the test steps to verify: Can be tested on Lenovo X1 following usual installation or nixos-rebuild ... switch
[ ] If it is an improvement how does it impact existing functionality? Increased usability and introduced functionality offered by common operating systems.