By using a character editor, like Valheim Player Editor (VPE) -that you can find on Nexus Mods-, you can change the appearance of your vikings.
This guide show the tags corresponding to each hairstyle and beard.
It has to be noted that female hairstyles are the same than male ones, with similar tags.

Hope that guide has been useful to some of you.
See you in the Mistlands, handsomes and cuties ! Skol !