One piece of equipment I see missing from the 1916 kit (though admittedly it probably wasn’t “issue”, more like improvised) is a trenching tool or spade with its edges and point sharpened. Besides the obvious earth-moving purpose, it also came in very handy as a close-quarter trench weapon...either for raiding (use it like a spear) or repelling a raid (use it like an axe).
The object above the Enfield’s receiver looks like a mattock sort of e-tool, the handle is next to the mace.