I had an idea for a shirt with Aoko and Miyako.
In the "Classic" stage with all the grass and the city in the background (overlooking view), Aoko is kneeling with a sly confident look on her face (The Aoko look of course!) to show Miyako, who is looking at her wares in a pondering expression (Think
with a finger to her mouth or something), the contents of her suitcase. Inside the suitcase is White Len and Dark Len cat form, with various orb/charm/NekoArc Paraphernalia piled around them. It is day time, and the suitcase is overflowing almost with goodies. In the background a Neko Arc could be flying, or Nanako could be floating in the distance.
The second idea was the same classic background (This time facing the grass and the hills, not the city overlook view), but only this time we don't use the suitcase (A mystery, the suitcase is...). Instead Miyako is standing over Aoko looking with a more surprised pondering look, who is currently working on a Shiki UFO Catcher doll of sorts (Maybe eyes closed... or half open for that suttle look). There are various charms and trinkets in front of her inculding the NekoArc stuffs, but as she's working on these wares and the stuff spread on the grass, we can either put normal form Ren/WhiteRen also overlooking Aoko working, or cat forms of both of them looking at the doll. This is more centric over the Shiki doll Aoko is working on, as opposed to Aoko dealing to Miyako.
So that's just a vision in my head. If you decide to do any of these and need more details as to what I mean, feel free to ask. If not, I'll probably be purchasing a Hisui/Kohaku shirt all the same.
~Chun