What you are asking for basically is requesting pixel art.
Because the smallest icon is 12 x 12, There really isn't any room for true art.
This is a basic rundown of what your smallest picture would look like.
Larger Version: (*)
And yes, it is to Scale.

Also, with those limitations, you can't make it cute or angry.

I would like a proper list of scales. Seriously, if you want it, you have to do your job and tell us everything we need.
Because 12x12 still requires pixels, your picture will ultimately be the same as pixel art.
I missed the 128x128 part, but there's no way for me to evenly turn 12x12 into 128x128, Because 128 divided by 12 results in fractions.
Also, what's vector? Never heard of it.

@Liminori
Vector art is very much different from pixel art. Bitmaps store information in pixels of an image, so that each dot has a color information. A vector image saves information of the image in vectors (like lines and points), so that, no matter what the original image is scaled to, the resolution when it's blown back up is the same.

The only vector art program I know of is Inkscape. Hope this helped!

Well, seems like the app would be useful whenever people want to download/check things out and not have suggestions or ads from google that relates to it. Though I do have a bit of question list:

1. Do both the art styles have to be the same or different on each port? Because I've seen some icons that differ whenever on either computer or Andriod, yet still base on the same concept.
2. Do you want detailed or cartoon style of vector based art? Some can be as though it looks as though the actual thing yet lined/shaded out and others are simple drawing full in or lined.
3. Are you looking for specific poses for the artwork and/or different 'modes' of the icon whenever things happen like error, scavenging, or starting up? It might be a little more work, though it's pretty neat, especially going with new things haven't done yet.

Well anyways, I'm done with questions now. Here's some examples that I've drew as a bit of a 'base' to get the thing going. The top two are pretty much for PC version, while the bottom is for Android. It goes a bit from top right, top left, and bottom with going down a bit realistic to cartoonish. (Btw sorry for LQ there; I kind of have a bad camera to use with my 3Ds pretty much. :S)

http://prntscr.com/3x7ofw

This here is my first time using inkscape so I definitely won't be surprised if it's not of quality you're looking for.
RaccoonPunk

Originally (once I thought I was finished), there was no eyeball and no smile. I figured the bottom was too plain but the little grin added a bit more character to it in my opinion. My sister suggested an eyeball and the iris around it was totally unexpected but it happened somehow and I like it. It is in svg format but the upload is png since imgur doesn't support svg. I can modify it however you'd like or I can give it to you to modify though I don't know anything about licensing. Good luck on your developing!

Well, I sorta assumed I could fix all the specs I ignored later if you liked it, but here's something I thought might be a bit closer to what you're looking for?

...though, Illustrator doesn't seem to want to export to SVG format, I don't know if there's a way around that...