Sometimes it can just be hard to get creative, or to get creative in the right context. Moodstream is an interesting new website from Getty Images that is a good way foster the right mood.
It is simple to set up what sort of mood you want: happy, sad, humourous or contemporary are just some of the options. Alternatively the presets wheel has six different options to get you started.

If a picture, music or video track takes your fancy it can be added to the Moodboard to find out more information about using the media.
Otherwise it is just a good way of being creative.