There are two sides to the bridge and I would suggest that Thirstforwine’s suggestion was great:
I’ll add to this a suggestion based on a sketch put together in 2014 by the same artist who brought us the Walrus , Aquarium, and Tyre Towers.
He did the sketch, I’ve amateurishly added some colour to bring it to life, but it is just a concept. I my view this would look great under the railway bridge or in the underpass:
Based on a design by http://aeroarts.co.uk/
The theme is a surrealist view from the Horniman, with a train on a rollercoaster, a mobile phone, a giant gherkin, a cheesegrater, an electric razor, a catherine wheel, and a couple of cruiseliners passing by. It is just a concept of what we could do with the space.