How can the HTML where the SignOn Event Message is displayed be changed?

I need to change the layout of the HTML page where the SignOn Event Message is displayed after a user logs in.  I need to change the layout to accomodate images.  As dilvered it works great for text but images are limited by the table layout properies. I would like to change the layout and subsequently add javascript to limit the when the message is dispayed by adding a cookie that will require the end user to have to click OK only once a day and any other login within that day be automatically directed to the home default page