0 A.D. is a great game, but very much a work-in-progress, hence full of mistakes. Here are a few things I noticed for a start. Undoubtedly there are more, I certainly did not go through all actors.
The catafalque's horse's manes and tail hair move independently:
Themistocles' helmet seems to be transparent:
Iphicrates' and Xenophon's shield go through their shoulder:
Philip the Pikeman is beheaded by his own shield when attacking:
The Kushite's pikeman's shield position is non-sensical when attacking:
Hopefully someone from the art team (@Alexandermb, @LordGood, @Stan`, @wackyserious) can have a look. For most people these things probably don't matter, but dotting the i's and crossing the t's is appreciated by some, myself included.