Linden, the Steadfast Queen
While gaining life is generally considered weak, white has certain triggers to capitalize off it, such as
Dawn of Hope, or
Well of Lost Dreams for card draw, and cards like
Archangel of Thune for pure damage/buffs. Linden's ability encourages going wide with the army to get maximum benefit, but the limit to white-only creatures means that some go-wide token making abilities from artifacts will generate less value. However, those cards may still be good includes, since you'll be running other cards that take advantage of going wide anyways, so some anti-synergy may be acceptable if the means are overall efficient. Triple white cost can be tricky if running too many utility lands, but it means that she can also add a bit to devotion-based strategies.
Syr Alin, the Lion's Claw
I don't know... Pauper maybe? There are generally better anthem commanders, but maybe if you want a super casual mono-W Knight tribal deck?
(?)
Kenrith, the Returned King
Technically a 5c Commander, due to his abilities, so I don't know if you want to list him - however - he only
requires white to play, and limiting the included colors can make for an easier mana base, while still being able to use his abilities with
City of Brass type of effects. It might be kinda cool to have a 'mono-white' aggro deck that happens to have access to on-demand haste and trample, with card draw in the Command zone.