I like the idea of this "seed garden," but it looks like it hasn't been used in a while. When I came across it, I thought, I should try to remember some of the ideas that have bubbled up in dreams. As I'm falling asleep, I try to focus on issues in my novel, hoping that my subconscious will come up with something--- it does, but never anything useful. I wake up involved in some other story that has nothing to do with what I'm working on (sometimes I even dream about the writing process, juggling scenes and editing). I can't seem to be able to train the darned thing to stay focused. So here are a few.
(1) A courtroom drama in which the antagonist has been stealing people's shadows (how? why? not sure). It's a class action lawsuit, and the aggrieved party claims that they own their shadows since their image and likeness is a part of their person, while the antagonist claims that shadows are external entities because they are an artifact of exterior light (perhaps even light that he or she provided as part of the theft). The case is decided in favor of the plaintiffs, but the point is moot because the defendant can't return the shadows anyway: they all got stuck together and you can't tell which is which anymore. Shadows are, by nature, indistinct. Once merged, you can't pull them apart.
(2) The zombie apocalypse can't get started because there are only four zombies and they won't be bothered to get out of their basement to infect the world. Actually, the basement belongs to the mother of one of them--- the college dropout was just living there until he could get a job, but got infected by the zombie plague instead. The mother sometimes comes downstairs to do laundry and yells at them to make something of themselves, but they're too busy playing video games. The smell of unwashed socks mingles with rotting flesh, and sometimes a pinkie or a jaw drops off. Then something happens (what?) to get them off their lazy, undead asses and out into the world, bringing it to a horrifying end. It's about bloody time.
(3) A female protagonist spontaneously transforms into a mermaid. This is followed by a frantic emergency room visit, but attempts to reverse the process fail and she's taken to the internment tanks that are society's answer for this sort of thing. It's all society can do, after all. (Much hand-wringing.) Somehow, this ought to lead to a Cuban-style uprising and revolution on the part of the mermaids, but the hard part is figuring out the what and the how, seeing as they can't get far beyond the water. I can't tell if this is Kafkaesque or the opposite of Kafkaesque, since the metamorphosis is into something of beauty, not a bug (can easily be swapped out for angel, fairy, anything fantastic and beautiful). This light and beauty is surrounded by the darkness of medical crash carts, military vehicles, and barbed wire. Although you could do something like this with vampires or warewolves, it wouldn't have quite the same contrast.
(4) Not a plot idea, just an image: a modern witch freely mixes technology with arcane magical artifacts. I don't mean in a cyberpunk way: I mean broken old TVs (it's hard to find the old ones with a real cathode ray tube these days) wired into heads of lettuce (rotting), nails, a 1930's poison ring, powder of a crushed peat bog man (stolen from a museum), and a baby doll lost on a train. It has to have been loved--- doesn't work otherwise. She's building this junky talisman in her bathtub and it dims the lights when it's on. It's not an invention, though--- it's magic, perhaps sympathetic magic (the attributes of the ingredients are vaguely related to the desired outcome). She (or he) lives in a bare-bones rented house in a bad part of town.
Do anything you want with these ideas. I would, however, be curious to see what becomes of them, regardless of how little they resemble the initial seed. I'll pass on more if I have any.