If you do a forum search, you'll find a thread on an Australian WW1 song, Dinky-Di. I didn't look it up to see if it should be of any interest to you.

Also, probably tangential to what you're looking for, the Irish war for independence coincided with WW1 (not so coincidentally "England's difficulty is Ireland's opportunity", the concern for other small nations such as Belgium, the resentment at recruiting) and this comes up in several Irish Republican and anti-recruitment (not necessarily anti-war per se!). Examples include "Come Out You Black and Tans" - "Show your wife how you won medals down in Flanders", "The Grand Old Dame Britannia" -

"You know we've got the Huns to quell
We need all our money for shot and shell
So you'll have to sulk and go to Hell
Says the grand Ould Dame Britannia"

and "The Recruiting Sergeant" -

"Come wind or rain and hail and snow
We're not going out to Flanders oh
When there's fighting in Dublin to be done
Let the sergeants and commanders go
Let Englishmen for England fight
It's just about time they started-o
And I wished him then a very good night
And there and then we parted-o"

There are two versions of "Johnny I Hardly Knew Ye" in the database. One is a straightforward anti-war song (as I know it he returned from Ceylon where the DT version has Ceylon), but the second is in the form of a WW1 anti-recruiting, pro-Irish nationalist song.

Is "Will Ye Go to Flanders?" (Scottish) from WW1?

"Will you go to Flanders, my Molly-o
Will you go to Flanders, my bonnie Molly-o
There you'll get wine and brandy
And stacks o' sugar candy
Will you go to Flanders, my Molly-o?"

proceeding to

"You'll see the bullets flying
The soldiers as they're dying
Will ye go to Flanders, my Molly-o"

It's on the DT, as are "The Fires of Flanders" and "I Would that all the Wars Were Done".

I don't know which of these were published. No post-WW2 material, anyway. And they must have been sung to have been passed on.

HTML line breaks added. --JoeClone, 11-Nov-02.