You may already know that i love the Outposts of Empire series, when I bought my John Vickery Rhodesia poster it also came with this beauty from the same artist which I now have for sale.
There are a number of fantastic British Empire related poster series in particular :
Outposts
EMB
Empire Exhibition 1924
One website which usually has a number of Empire posters to view and buy is
I would encourage you to go there and take a look !