I have no other mods installed. It's a Steam install of Legendary Heroes. I also have no other DLC installed.
I installed all of Children of Storm-1850-1-8*c. To be fair, I installed Stormworld first, then deleted all the mod and map files before installing Children of Storm.
The thing I'm not sure about is where the png files the xmls are looking are supposed to reside. I have a few png files, but not the ones the mod is looking for. For example, CPELF_Hedge_Inside_03_shadow_256.png is not in the mod install location. I'm not sure if that particular file is relevant, but others are missing too.
Children of Storm-1850-1-8*c.rar\Gfx\ChildrenOfStorm\ExpandedFactionsLH\Elves\SubsetBuildings\ contains one png : EnvironmentPlants2.png
This also happens on the gnome buildings.