Update: This script only works on current beta "Precise Pangolin". The changes will persist until some unity update overwrites those qml files again. Re-running the script will help then.
As we all know unity 2D currently lacks an option to configure the size of those launcher icons.
It is possible though to achieve this by manually editing some qml files. This is quite annoying, so I put a script together that takes care of it. It doesn't rely on line numbers but has some very simple "logic" to be able to handle possible line shifts in the future.
Coding style is of course horrible, and not many possible fail cases (e.g unity 2d is not even installed...) are taken care of.
Only thing it really does is backup those qml files before overwriting them.
Maybe somebody considers this useful...
1) Save script somewhere you like
2) make it executable (chmod +x script.py)
3) run as: script.py iconSize (e.g. script.py 32)
Don't forget to restart your launcher. Killing it might be sufficient, logging out and in again works for sure.
I don't have any clue whether such a script already exists, but here is mine
Having such a script polished and then integrated into one of those fancy unity configuration programs may be an interesting option as long as Unity 2D lacks this feature.