Right Now by Van Halen is a very good piano song. When played solo on piano it is very easy to listen to ans well as catchy to the listner. Since Billy Joel composed most of his songs on piano they are also good when played solo by s pianoist.
It depends what you're into really. Personally I like Mellon Collie & The Infinite Sadness by Smashing Pumpkins, though for a wedding you'll probably want more of a classical slant and therefore Brahms' Piano Concertos would be more suitable.