Personally I find the name "Generic Fixed Set" really grating. I would prefer if we could rename the page to something like "Miscellaneous Set" or even "Miscellaneous Cards" seing as how they're not part of an official set or anything (yet). (I'd be alright with Generic Fixed Set being a redirect link.)
In terms of template coloring used for the set, it's hard for me to tell based on the blurry pictures of cards so far, but the bottom-right icon appears to be a mix of blue-ish and purple-ish in color, with a bit of lightish pink surrounding it. We're kind of using all three of those colors for different sets, so I was thinking we might as well use the "Default" color code for the templates for this not-a-set.
Miscellaneous is too long to type, I prefer Generic. Plus, I already set up all the templates that way. Feel free to change it all if you really want.
For the color, I already set them up using Template:ColorCodeValues/GenericFixed and Template:RGBValues/GenericFixed with middle-gray. Feel free to edit it. I agree that the colors on the icon are all already used by the other sets.
Something that means "Not belonging to a set", so "Singleton" Set might be good (assuming they don't include more than one in a box/tin/etc ever). "Merch Promos" is pretty descriptive, but might confuse with the earlier merch/tins containing cards not in this set.
It's not the end of the world if we can't think of something, hopefully by the time more of these cards get released there'll be an official name to go with a checklist or something. They'll also have to give the cards some kind of set identifier once the OCR revision with them is released.
That Facebook thread may be the best place to influence what that name might be. Since the devs at this point just called it Generic Fixed symbol there. I think bringing it up there might be good, maybe suggest the best you like from here?