I'm not to be held responsible for possible bricking of your device. You do this at your own risk and my only warranty is that it worked for me when I did it. If it didn't for you, I'm sorry.
With that out of the way, this is a modified script and method I found on the International forum. Thanks to chrisch1974 for the initial guide. I needed to make changes to a couple things to get it working for us, I'm usually pretty uneasy about messing with BOOTLOADER stuff, but, I really wanted to change my splashscreen, dammit! So I pretended I was a lab rat and took one for the team.
S-OFF (alternatively, Revone, which is what I used.)
EZ Splash Screen Flasher and Image Converter (click link and download, might want to read a little about how to use it as well, it's not hard, but still.)
splash.zip provided at button of post.
Preparing the image for flashing:
Find a picture you want to use, any picture just as long as it's 1080x1920 and either BMP, PNG, or JPG as EZ Splash Flasher won't convert anything else.
Start EZ Splash Flasher by double-clicking CLICK-HERE.bat, make sure you put your image in the "place-image-here" folder and convert it. Depending on the format, make sure to follow the instructions in the script as it will tell you which option to choose. Once it's done, rename your converted file, which should be custom.img to splash1.nb0
Download the splash.zip I've provided and replace the splash1.nb0 inside with the one you just renamed.
I've already modifed the android-info.txt file to work on the Sprint variant, even if you recently SuperCID'ed your phone, this will work.
How to flash it:
First things first, we need to get into Bootloader, you can either hold power and Vol- or use adb and this command:
adb reboot bootloader
Next, we need to get into the RUU Flash mode. You'll know you are in it because it's a black screen with the silver HTC logo and that is all:
fastboot oem rebootRUU
Now, we are going to flash the file:
fastboot flash zip splash.zip
It will run through a few things and should finish without any errors. On mine, there was a progress bar that popped up on the phone, but it never finished filling up. Yet, the fastboot command finished without errors and put me back into the command prompt.
You are DONE!
Now issue this command to reboot your phone:
Enjoy your new splash screen! (if there was no errors, obviously.)