Never really been happy with my boot screen, so this is the easiest way I found to change it. Also made the boot screen from a wallpaper, wasn't too happy with any of boot screens I found.
1. download the program which includes a stock image.
2. unzip it
3. click RUN THIS ONE.bat
4. Press 1 to convert the BMP to IMG (if you want to change the image to your own, change the splash.BMP to your own image (must be the same file name and be 480x800)
5. Press 1 begin putting the image on your android device
6. reboot your device to the bootloader (instructions give more detail if needed) then Press Any Key
7. Plug USB cable in then Press Any Key
8. Ensure device is listed at top of window and press 1 (if not: ensure usb cable is ok, phone is at bootloader, drivers are installed)
9. Device should install image, reboot.