I couldn't find any post talking about this so I decided to do some digging and found a way to have custom bootscreens. (Pretty sure it works on every kindle released as long as its jailbroken)
WARNING: This involves doing things in root (/) so only do this if you know what you are doing and are not afraid of bricking your device. 
Anyways heres how to do it:
First make sure your kindle is jailbroken and has USBNetwork installed.
Then ssh into / or run "cd /" on your kindle like you would normally do with the extension.
Now make sure you have sftp installed and mount your kindle on.
Now head to /usr/share/blanket/* (The * represents all folders)
All the folders you see in that directory are self-explanatory, download whatever default boot screen you want.
Change it in your desired image editor and then upload it back with the
SAME filename.
Optional: Backup the default/original boot screens for future reference or if you want to revert it to normal.
Hope you enjoy!! I found this interesting to me so hopefully it is the same to you guys.
