Where is the gray Apple logo shown on system startup stored in OS X Mavericks? I'd like to change that image. I know there's BootXChanger that works on older versions of OS X, but it doesn't work on my Mavericks computer.
It's not just as simple as that. As the system boots, it loads the first partition, which just happens to be the EFI partition. This holds the firmware for booting the machine. The Apple logo is stored in this firmware. Modifying it is theoretically possible, but for someone other than a senior Apple engineer it would almost certainly brick the computer. Better just sticking to the boring grey logo. This post here talks about the startup chimes and the same applies to the logo.