Hey there,
Happy to have found this new os & community here 
I installed the distro on a usb drive with a separated /boot partition on (hd0,msdos1).
When the VM boots, I get this:
error: file `/boot/grub/themes/netrunner-black/theme.txt' not found.
Press any key to continue..._
Then, I looked for the file:
grub> ls (hd0,1)/grub/themes/netrunner-black/themes.txt
theme.txt
grub> echo $root
hd0,msdos1
So indeed, grub is looking in the wrong place, it should look in $root/grub/themes…
Fixed in /etc/grub.d/06_netrunner_theme
34 [-]echo "set theme=(\$root)/boot/grub/themes/netrunner-black/theme.txt"
34 [+]echo "set theme=(\$root)`make_system_path_relative_to_its_root /boot/grub/themes/netrunner-black/theme.txt`"Then re-generate grub.cfg:
grub-mkconfig -o /boot/grub/grub.cfgAlthout the theme is still messed-up, that’s most likely because runned by the VM.
See ya