If you create a bmp file with the same name as you mdb, and place it in the
same folder, Access will show it as the splash screen. It may go by too fast
though.
Another idea is to create a form in Access, and set it as your start up
form:
Tools | Startup | Display Form/Page
You can use the Timer event of the form to open another one and close the
splash form by setting the TimerInterval to (say) 2000 (milliseconds).