Thanks to Becky Kitchen for the tipoff to this tool which she saw in use today. Flinga is a Finnish web-tool, which is a little like Dotstorming, which I have shared here before. It's a collaborative space to which people can be invited. 

Using a QR code or a unique URL, people can contribute to the board, or grid by flinging stuff there... This can be text or media including images. Users can then vote on particular images or text, which is placed in cards on a grid and can be positioned using a number of options.

Worth a look. It connects with Google accounts very smoothly....