Looks like a fun deck. A was thinking of making a token/lifegain deck with Trelassara, moon dancer. But I think Shanna is a fine commander for such a deck as well.
I miss a few cards for gaining life. I saw only three or four of those cards. I'm missing the 'soul sisters'.
Soul warden, soul's attendent,
essence warden,
daxos, blessed by the sun for lots of lifegain triggers, that way your payoffs like Heliod and
ajani's chosen and such will trigger much more frequent. If you are leaving the lifegain plan entirely that makes sense with your commander. In that case Maja, bretaguard protector could be a fine addition, it's an anthem and tokenmaker on one card.