just some quick notes on theming Kali, nothing fancy.
wallpaper is located in /usr/share/desktop-base/wallpaper/contents/images (2560x1600.png, 3840x2160.png)
lockscreen could be defined in /usr/share/desktop-base/kali-theme/lockscreen/gnome-background-xml
gnome-background.xml
<background>
<static>
<duration>8640000.0</duration>
<file>
<size width="1024" height="768">/usr/share/backgrounds/kali/kali-contours-4x3.png</size>
<size width="1280" height="720">/usr/share/backgrounds/kali/kali-contours-16x9.png</size>
<size width="1280" height="800">/usr/share/backgrounds/kali/kali-contours-16x10.png</size>
<size width="1600" height="1200">/usr/share/backgrounds/kali/kali-contours-4x3.png</size>
<size width="1920" height="1080">/usr/share/backgrounds/kali/kali-contours-16x9.png</size>
<size width="1920" height="1200">/usr/share/backgrounds/kali/kali-contours-16x10.png</size>
<size width="2560" height="1440">/usr/share/backgrounds/kali/kali-contours-16x9.png</size>
<size width="2560" height="1600">/usr/share/backgrounds/kali/kali-contours-16x10.png</size>
<size width="3840" height="2160">/usr/share/backgrounds/kali/kali-contours-16x9.png</size>
</file>
</static>
</background>
login is set up in /usr/share/desktop-base/kali-theme/login background & background.svg
grub boot screen is located at :
/usr/share/desktop-base/kali-theme/grub/grub-4x3.png & grub-16x9.png, and grub_background.sh
grub_background.sh
WALLPAPER=/usr/share/desktop-base/kali-theme/backgrounds/background.png
COLOR_NORMAL=white/black
COLOR_HIGHLIGHT=black/white
Make symlinks in /etc/alternatives called :
desktop-background, desktop-grub, desktop-login-background, desktop-lockscreen.xml
Some custom graphics, and playing around with these files and symlinks, should give custom graphics settings :)
Desktop menu files are in /usr/share/applications & has the format kali-softwarename.desktop
Kali specific menues are in /usr/share/kali-menu/applications
I /usr/share/kali-menu, there's also a shell-execute script for executin shellscript based tools...