Add the possibility to have different textures for the same unit. This is useful for example in the case of the Indian faction: it would be great if the teepee could have different drawings, instead of all be looking the same.
Those could be set in the XML file, and there could be a 'probability' property also: the highest one, has more possibilities to be chosen. This could be either in % or just typing a free number and calculate the % from the highest.