Ysgardian Commoners include peasants, serfs, servants, farmers, the elderly, artisans, and hermits.

All those of the Viking faithful who - while, no, not actual live-to-die Viking beserkers themselves - have, nevertheless, made it to Ysgard.

How? Well, chances are they died defending their village from raiders, or they went on some fool quest themselves, sick of the snubs and ridicule they had suffered up until then.  Regardless, however it happened, they died in battle. And everyone knows, if you're a Viking...

Die in battle, you gets you some Ysgard! 

That said, they're not living that fight all day, drink all night, tankard life. They're the ones serving the ale, swabbing out the ale halls and so forth. 

Doesn't make them a pushover.