postmarketos-ui-{xfce4,mate,lxqt}: wallpaper was removed

Describe your issue

What's the expected behaviour?

Having a wallpaper background image.

What's the current behaviour?

MR !4805 (closed) removed /usr/share/wallpapers/postmarketos.jpg and broke several background image implementations.

Xfce4 wallpaper & lockscreen background:

• https://gitlab.com/postmarketOS/xfce4-phone/-/blob/0.5.2/config/xfce4/xfconf/xfce-perchannel-xml/xfce4-desktop.xml

MATE wallpaper:

• https://gitlab.postmarketos.org/postmarketos/pmaports/-/blob/0bb531b926ccbb3b0bcad8f3a4de0459543dc3d9/main/postmarketos-ui-mate/000-system-background.gschema.override

MATE lockscreen background:

• https://gitlab.postmarketos.org/postmarketos/pmaports/-/blob/0bb531b926ccbb3b0bcad8f3a4de0459543dc3d9/main/postmarketos-ui-mate/001-screensaver.gschema.override

LXQt wallpaper:

• https://gitlab.com/antoni.aloytorrens/lxqt-tablet/-/blob/0.3/config/pcmanfm-qt/lxqt/settings.conf

LXQt lockscreen background:

• https://gitlab.com/antoni.aloytorrens/lxqt-tablet/-/blob/0.3/config/xfce4/xfconf/xfce-perchannel-xml/xfce4-desktop.xml

How to reproduce your issue?

What device are you using?

qemu-amd64

On what postmarketOS version did you encounter the issue?

• edge (master branch)

• v23.12

• v23.06 (supported until 2024-01-18)

• I confirm that the issue still is present after running sudo apk upgrade -a

On what environment did you encounter the issue?

Environments

• GNOME Shell on Mobile
• Phosh
• Plasma Mobile
• Sxmo (Wayland/Sway) Please post the output of sxmo_version.sh
• Other: xfce, mate, lxqt

How did you get postmarketOS image?

• from https://images.postmarketos.org
• I built it using pmbootstrap
• It was preinstalled on my device

What's the build date of the image? (in yyyy-mm-dd format)

2023-03-24

Additional information

none