Tate Modern have launched a blog inviting the public to submit images & ideas to help them "create a photographic 'Mood Board' of the kind of interior spaces, ambience and designs that people would like to find" in the Herzog and de Meuron-designed planned extension.
Currently the blog features "posts" by Jacques Herzog, Nicholas Serota and Culture Secretary James Purnell. It'll be interesting to see what the take-up is like: the "best photos and ideas" will be displayed at the Tate next year.
A more low-tech way of approaching this would be just to put comment boards up in the gallery, and allow visitors to scribble ideas, tack up images, or draw. An interesting idea Auckland Art Gallery and City Gallery Wellington could look into for their redevelopments, as a way of engaging their audiences.
Image from the Guardian website