I opened a Fidelity account, and Quicken changed its splash screen to a Fidelity logo.
When I got rid of the Fidelity account, Quicken did not change the splash screen back to normal.
I figured out how to do it.
Go to C:\ProgramData\Quicken\Config\QUICKEN.INI
Look for the setting called Splash=
Change that file to anything you like.
The standard Quicken splash screens are in: C:\ProgramData\Quicken\Sku