Thanks, but I know how to change the plymouth resolution under Ubuntu precise:
edit /etc/default/grub and uncomment this line and put resolution you want for plymouth here:
# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
But why it is not supported by default by Nvidia when I install their drivers?
Do you think my grandma, when she will update their nvidia drivers (in fact she just knows to launch ubuntu update wich will update nvidia driver) will think edit the grub option to enable higher resolution?