You can create your own boot animation for your device. The Android platform provides an easy way to replace its default boot animation by putting a file into /system/media/.

To create your own file, see How To Change, Customize, and Create Android Boot Animation.

How to install the boot animation:

On the host, use the ADB to download the file into the device.

For example:

$ adb push ~/Downloads/ /mnt/sdcard

On the device, remount the /system to writable, and copy the file:

$ mount -o remount -w /system
$ busybox cp /mnt/sdcard/ /system/media/
$ mount -o remount -r /system