Ubuntu 20.04 boot logo image directoy

Solution 1:

A basic search results that the ImageDir is /usr/share/plymouth/themes/spinner

[Plymouth Theme]
Name=BGRT
Description=Jimmac's spinner theme using the ACPI BGRT graphics as background
ModuleName=two-step

[two-step]
Font=Ubuntu 12
TitleFont=Ubuntu Light 30
ImageDir=/usr/share/plymouth/themes/spinner

It is not good idea to replace lot of Images of this spinner..

Instead find out a simple Plymouth theme which uses single Image and replace it..

If you want to change Ubuntu logo..

this is the Image file

/usr/share/plymouth/themes/spinner/watermark.png

Solution 2:

All plymouth data and config needs to be embedded inside initramfs to be applied in iso boot, so you need to apply:

update-initramfs -u

Try this and check the results.