I think the spearmen sprite have already shield on some frame specially on walking one ( I also think it will also be difficult to add shield on all frame without redo all the pose model that mean redo all the model )
maybe we can try to use the age of wanders 2 sprites
for multiplayer I think you have to overwrite a sprite with the same index ( ex:0x007e is the index for gruinf.spr and can work for 0x007ecorsaire.spr)
so 0x007ecorsaire.spr + 0x007edarklancer.spr +0x007efurieoldant.spr can overwrite all this sprite ( GRUINF/GRUXBW/OUTINF/IMPGRT/ARTILL/NGOB/NGARCH/ORCBOY/BIGUNS/MUMMY/SKELWR/WIGHT/BANSWD )
and 0x010awarhydra.spr an overwrite ( 010a = DWARF/GHOUL)