I see your point, but... if you depict a XYZ warrior wearing XYZ traditional dress... while fighting an undead monstrosity, you'd need to make sure that mechanically, the XYZ dress has the same mechanical protection than the full plate. Because if there is a difference, wearing anything except than the best available armor in the picture makes the XYZ warrior look less advanced, which is also something you'd want to avoid.
When I look at the second picture, I see people who lack any metalworking technology to make armor, fighting with an obsidian-incrusted wooden club instead of more modern weapons... It evokes stone age fighters. So unless the macuahuitl has the same stats as a greatsword and the traditional dress is worth a steel armor, beware of unwantingly reinforcing stereotype of "meso-americans = less advanced".
BTW, both pictures are great art.