CustomLogo
<key>CustomLogo</key>
<true/> OR <false/> OR <string>Apple/Alternate/Theme/None/Path</string> OR <data>PNG/BMP/ICNS base64 data</data>
Enable the drawing of the custom boot logo.
true - Uses the default boot style, Apple.
false - Disables custom boot logo.
Apple - Use the default gray on gray apple logo.
Alternate - Use the alternate white on black apple logo.
Theme - Use the theme boot screen for entry type - NOT IMPLEMENTED.
None - Use no logo only background color, gray if not specified by custom entry.
Path - A file path to load a custom image from
<data> - A base64 encoded PNG, BMP, or ICNS data.
If no option is specified then the boot screen will be drawn only for >= 10.10 Yosemite, so it remains compatible with previous behavior.
The CustomLogo key can also be used under GUI/Custom/Entries in conjunction with BootBgColor for a different screen for every OS. However, the graphics output protocol is not in anyway modified so if the OS draws after it is started then it is after the boot screen is drawn and will overwrite the custom logo, at least for now.