There's an exhibition at the London Transport Museum on the new ELL.

http://www.ltmuseum.co.uk/whatson/128.aspx

'Overground Uncovered: life along the line, celebrates the new London
Overground line - London's first major public transport development for
over ten years. The exhibition explores over 160 years of history and
innovation behind the building of the new line and Brunel's Thames
Tunnel, and provides a snapshot of cultural highlights along the way.'

E.