Maps for the Complete version of Heroes of Might and Magic III (including Shadow of Death). Will not work with the Ubisoft version. Recommended way is the gog.com version of HoMM3 Complete, then using the free community based heroes3hd patch below:
https://sites.google.com/site/heroes3hd/eng/download
No, this is not the Ubisoft version of Heroes of Might and Magic III, that doesn't contain Armageddon's Blade and Shadow of Death. Maps listed here need the expansions.
Installing a map: just copy the .h3m file to the Maps/ directory found in "Program Files", example:
cp midlands_and_dragons/Maps/Midlands\ And\ Dragons.h3m ~/.wine/drive_c/Program Files (x86)/GOG.com/Heroes of Might and Magic 3 Complete/Maps/