Heres one of the ways you can change the default splash screen that appears after login.
1. Install gTweakUI from synaptic(Click System>Administration>Synaptic you’ll find gTweakUI on the list of applications there)
2. You can use a splash screen image of your own or search for some on the internet, i used one from Gnome Art. Once you’ve found yourself a splash screen, you’ll need to save it somewhere, i saved it here:
Thats where the default splash screen is saved.
3.Now we’ll use gTweakUI to change to the new splash screen. Go to:
You’ll see your current slash screen displayed there, click it to change to the new splash screen. You will have to select the new splash screen from where you saved it. Click close and you’re done! Log off and log back in see the new splash screen in action.