In London Victorian Streets there are three Peabody Squares listed, as follows:
Peabody Square: Islington N.1
Peabody Square: London Road, ST.SAVIOUR SOUTHWARK
Peabody Square: Blackfriars Road, Bermondsey SE1.
There are a number of Peabody Buildings listed here, though none for Shadwell.
This site might be useful www.englandpast.net/
and you might find photographs there.
The site you have been given for Peabody Trust has an e-mail address, it is possible they could help you - I hope they are helpful as I have e-mailed them with a query!!