Hi there,
ICM have two Great War figure kits, one British the other German.
Andrea have a very nice charging British figure which comes with two heads, one with a gasmask on.
If you go to the Perth Military site, have a looksy under their news section for Toro models.In the last day or two they have released a 3figure trench dio in 1/35 scale.
Verlinden also have a two figure trench dio which i think was just released.
Warriors also have a couple of W.W.1 figures i believe.
Aside from what else has been mentioned, some stores might have figures from Tauro.I think the Tauro has closed shop..they had some very nice Great War figures in a variety of poses.
I'm currently working on a Great War dio myself with a MkIV from Emhar, so i know what the situation is like trying to source figures!
Best of luck,
Shay