Totem Spirit:
-Do the elk thing that adds 15 ft to your movement.
It's already legal, so you don't have to worry about balance, and in addition to giving you a more
cunicular move rate, it will also help your jumping ability. See, jump distance is based on STR, and as a barbarian that'll already be pretty high. But your max jump distance is still limited by your max move rate. This'll allow you to complete a full long jump while raging and still have some movement left over.
Aspect of the Beast:
Several ideas-
-You gain the luck of a rabbit. Once per day, after seeing the result of an ability check you made but before knowing if it succeeded, you may choose to reroll that check and use either number.
-You gain the charm and guile of a rabbit. You add twice your proficiency bonus whenever making a Persuasion or Deception check, instead of any proficiency bonus you usually apply.
Both are simple ideas based around the mythology of rabbits that should make for an interesting utility. Alternatively:
-You gain the ears of a rabbit. You can hear moderate-level sound up to two miles away (yes, this is
biologically accurate for rabbits), such as the approach of humanoids or the early signs of an oncoming storm. Additionally, You have tremorsense out to 30 feet.
Totemic Attunement:
-While raging, you have a burrowing and climbing speed equal to your current walking speed. You are capable of digging through terrain made of loose earth or softer, and you leave behind a tunnel big enough for a creature of your size to squeeze through.
Keep in mind that next level you'll gain Persistant Rage, meaning you can keep rage-digging as long as you want or until you fall unconscious. Alternatively:
-While raging, once per turn, if you score a critical hit or reduce a creature to 0 HP with a melee attack, you can move up to your speed.
This can be flavored as a sort of leaping around the battlefield, tearing apart one foe and immediately jumping to the next. Like the
Monty Python bunny!