https://tidsskrift.dk/kuml/article/view/24902
It has been speculated that the statue was covered in clothing
Tacitus' Germania has an interesting passage regarding the cult of Nerthus, which may hint at that as well (Or just a cloth covering the chariot?)
Regarding antlers or animal heads on statues, i could not find anything about it.
Antler seem more associated with celtic deities.
In later germanic mythologies most of the gods are human in appearance (Although there are couple depictions of figures with horned headgear).