I think you mean authenticate the kernel. Is that correct? If you want to do that, U-Boot has that capability. You can do all of this in a script that will either boot the authenticated kernel or display a splash screen.
For the splash screen, there are several ways to do it. One way would use a U-Boot command, depending on version, to display a bitmap stored in flash or on an SD card. The other way would require you to convert a bitmap to a header file and rebuild the U-Boot image. I can give you directions for this if you tell me where you want to store the image and what version of U-Boot you are using. Also for rebuilding the image, you will need to know which source you are using, so you can add the header with the bitmap. Also what is the data format for the display (RGB 565, Etc.)?
Where is the kernel going to be stored and by what method are you going to authenticate it?