To remove it you can remove the usplash package. To replace it you need to get your hands on another usplash theme... and then follow a series of very tricky things. Have a look at the Bea->Bianca upgrade guide in the Wiki to see how to change the theme.
Can't understand why you would get rid of it. But I think that the black box in the middle does not really fit into the Bianca design theme.
And don't cry for that I know (the hard way) how difficult it is to get something like that pretty...
Don't fix it if it ain't broken, don't break it if you can't fix it