Do you get a penalty if you just never stand? Is that a thing or no..
No… There’s no additional penalty. You’ll just sit there the entire rest of the game I suppose.
18.104.22.168 - When there are ten (10) seconds remaining on the penalty clock of a penalized skater, she will be instructed by the penalty timer to stand. She must stand.
From the WFTDA Standard Practices:
The Penalty Box Official shall inform the skater who is refusing to stand that the remaining time of her penalty will not be timed until she stands.