I was thinking of using Autumn/Spring Courts as the subtle cousins to Winter/Summer. To contrast the Winter/Summer, they would encourage transitions between the seasons, have patriarchal leaders, and not be bound/sworn to attack their opposite (probably dislike them, but realize they are necessary). These subtle Courts are less renowned because they do not follow the extremes of their sister Courts, but could potentially be as nefarious when it comes to maintaining the cycle (IE the Erlking's rampages). I was thinking of using the Erlking the Father/King/Prince (most likely Prince) of Autumn. Perhaps Santa Claus could somehow fit a spring motif.
I'm playing a former High Sidhe of the Autumn Court in a game. This is how I've done it.
[-4]Summer (Seelie Magic- satisfies the catch against Autumn and Winter)- wildness, growth, renewal, birth, fire
[-4]Winter (UnSeelie Magic- satisfies the catch against Spring and Summer)- decay, slumber, death, entropy, ice
[-4]Autumn (AbSeelie Magic- satisfies the catch against Spring and Summer)- decay, slumber, death, entropy, earth
[-4]Spring (AdSeelie Magic- satisfies the catch of Autumn and Winter)- wildness, growth, renewal, birth, air
Basically, spring brings summer and thus AdSeelie. Autumn brings winter, thus AbSeelie. All of the powers other than fire and ice are also associated with spring and autumn from summer and winter, respectively. To balance it, fire and ice needed to be replaced. Since Autumn is typically associated with earthen colors and spring needed a unique element, I just gave them earth and air, respectively.
This is freaking awesome! Very similar to what I had in mind for adding Spring/Autumn magic. I would probably alter it slightly to fit the paradigm I'm trying for. Something like:
[-4]Spring (AdSeelie Magic- satisfies the catch of Autumn and Winter)- renewal, birth, warmth, peace, earth
[-4]Summer (Seelie Magic- satisfies the catch against all other Courts)- growth, chaos, knowledge, abundance, fire
[-4]Autumn (AbSeelie Magic- satisfies the catch against Spring and Summer)- death, hunting, harvest, cleansing, air
[-4]Winter (UnSeelie Magic- satisfies the catch against all other Courts)- decay, slumber, entropy, law, ice
I think this could lead to some very interesting politics/personalities in Faerieland.