Scandinavians developed primitive skis at least 6,000 years ago, though ancient Russians may have invented them even earlier. By the Viking Age, Norsemen regarded skiing as an efficient way to get around and a popular form of recreation. They even worshipped a god of skiing, Ullr.
If we're getting a food called eyescream I think skiing wouldn't be too silly.
Racing down steep snowy inclines would be fun but potentially dangerous due to high speed collisions. Skis would also make traversing large flat areas faster and cost less stamina.
I'm not sure how melee combat would work if at all, but archery could be fun on skis (think legolas at helms deep doing the stair surf).
They should also have an equip/unequip animation so they aren't OP. Imagine getting ambushed by a pack of wolves while slowly crossing a field of snow. You would be vulnerable during the unequip and this would add a layer of meaningful decision making when exploring snowy biomes.
Maybe they would be sold by the merchant? I'm not sure if it would be an accessory or a tool or.. go in the boot slot? No idea.
It would be really cool if they did something with this.
Source: https://www.reddit.com/r/valheim/comments/pj0cma/ullr_god_of_skiing/