De acordo com as notas de lançamento:
Black splash screen
In Linux Mint the boot splash screen is completely black. This is by design. Once the system is installed the boot sequence is relatively fast. The black loading sequence doesn't look out of place and it looks consistent across all computers, whatever driver you're using.
If you'd rather get a splash screen you can select one by typing the following command and selecting mint-logo:
sudo update-alternatives --config default.plymouth