It's the header on google.co.uk today - 4th March. They are obviously violins but I don't know if there's any connection with violins and the 4th of March. You'd think there must be or why would they be there?
It doesn't really matter, though. Yet again, google has come up with a cool logo. :o)
Editing to add - Jo has informed me that hovering my mouse over the logo tells me that it's Vivaldi's birthday today. So, the 4 violins are to represent Vivaldi's 4 Seasons. It's brilliant!