If you get hold of a book like Brophy and Partridge, The Long Trail, not only will it give you plenty of material, but if you look at the tunes the soldiers were utilising, they are of the popular songs just prior to the war. This has recently been reissued so should be easy to get hold of. Many of them would have been American tunes as American pop music had a big influence in Europe at the time, as well as the fact that Canadian and American troops brought songs over with them.

Here's a good one that was still being sung in pubs in Britain in the 60s 'My Brudda Sylvest' from 1908. I also think that the 'Died for Love' song was brought back over here by American troops during this war. It originated in Britain but this particular oekotype was crystallised as 'The Butchers Boy' in America.