Chris, nowadays there are lots of special schemes applied to airliners, from the most basic advertising (EasyJet) to very intricate and elaborate ones (South African, British Airways, Qantas to name but three.
There seem to be two distinct 'schools', the first one being advertising and this has allowd us to see a Concorde in Pepsi colors, a Swissair plane in a all-red McDonalds scheme (yes, the fast-food company!), Japan Air Lines planes with Disney characters painted all over the fuselage, or even 'Simpsons' planes for example. The other 'school' tend to favour promoting a particular trait of a country or a particular event and this has seen Air France aircraft decorated with soccer players during the 1998 World Cup, Austrian aircraft with faces of famous Austrians (incl. Arnie, of course!), Qantas aircraft decorated with Aboriginal artwork...