Pretty well zero Civ3 (or Civ4) mods are "meant to be played on a Mac", since none of the major mod makers run Macs; Civ3 Complete for OS X didn't even exist when most of them were written; and none of the mod making software is native to OS X.
If the error message quoted in the OP is exactly as it appears in the error message then it indicates that Civ3 was looking for a file called InfantryDeath.flc in Art/Units/Infantry/, because the '../' means go up one level from Art/Units/British Indian Inf WW1/. You could try putting a copy of the entire Infantry/ folder from Civilization 3 Game Data/art/units/ into Scenarios/AoI/art/units/, but I'll make no guarantees, and you may simply move the problem on to another unit or building that requires access to standard Civ3 art.
Aspyr attempted to ensure that several possible search paths were checked when looking for files specified by mods - and the Rev A patch tried harder than the original version, so make sure you are running that patch. However, these efforts have proved less than 100% successful, resulting in the kind of problems you are seeing when running mods in Civ3 Complete. Solving these problems is made more complex by the fact that the software has probably searched several places to look for Infantry/, and the error message may not be reporting a correct path. So we don't know for sure where we really need to put Infantry/ for it to find it.
You may also find that some mods work better in Conquests Game Data/Scenarios, and others need to be in ~/Documents/Civilization 3 Complete/Scenarios/
I'll download this mod and see if I can throw any light on the solution. Am I right in thinking the main post for this mod is
here?