Adding a GRUB2 background image and custom font

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http://askubuntu.com – I am trying to use grub-customizer to add a custom background image and use the Ubuntu Condensed font. The preview looks fine: But when I actually boot up, I get a messed-up configuration. The text is messed-up, with "unknown character" symbols appearing for the box around the boot menu options (because apparently only the default grub font has these special characters?). There is only a black screen as the background. I'm trying to use a 1366x768 (same as my screen res) .png as the background image. This should be compatible, right? What can I do to get a background image working? ( (HowTos)