To remove logo from welcome screen:
locate the file ‘ OOBE.xml ‘ right-click on it and open with WordPad
locate the line that said
*this sample is for the Dell_bar.png logo.
just delete the line or edit it make your own logo and point the path to it.
System information logo needs to be in *.BMP format and 120×120px in dimension.
The Welcome screen logo need to be *.PNG transparent background and around 250×30 because of the space.
The Media Center Logo is *.PNG format, transparent background and around 120×120px .