Player icons for iPhone game

We need new icons to represent types of player for our iPhone game (vConqr). There are four types - one human, three A.I.
Icons should work well at 32x32 pixels

http://www.vconqr.com

vConqr is a turns based strategy game for iPhone and iPod touch (read more at http://www.vconqr.com).

We're currently overhauling the menus and player setup screens and need new icons to represent player types. There are four types:

1. Human player
2. Easy A.I.
3. Medium A.I.
4. Hard A.I.
Note that in future we may add more A.I. types, so a scheme that can be extended is preferred.

Here's an early version of the new player setup screen, with the old icons: http://pan.europe.googlepages.com/v…layers.png

For reference, the old player screen looked like this: http://pan.europe.googlepages.com/v…layers.PNG

The new one is still in progress, but any changes should not greatly affect the context of the icons. The only probable impact would be that that background image will change, so don't try to match the colour scheme (ideally the icons should be neutral colours anyway).

- We intend these icons to be set on a white background, but icons that work well against other backgrounds too are preferred. Neutral colours/ black & white are best
- We want the three A.I. icons to be distinguishable and imply their relative levels in a reasonably universal manner. I had in mind computer icons (along the lines of the current ones), but with anthropomorphised screens with cartoon faces. Easy is happy, medium is neutral and hard is angry. But that's just an idea - don't be limited to it.
- Work well at 32x32

- Busy or fussy images
- Too much colour (if any)
- A.I. icons that are hard to decipher the level of, even after explaining