I think it's not possible, I read about it somewhere in this forum..
The maximum available resolution is 1250x790 - or something like that :-)
If you are using mac (as I can see from your screenshot) I can suggest "screen zoom":
while pressing "ctrl" key go up and down with two fingers on your mouse touchpad (or turn your mousewheel).
See also this post:
http://machinarium.net/forum/index.php/topic,1381.msg6509.html#msg6509I think that you will lose some quality but the game area will be bigger.
It's a trick you can use also with other games and apps.
Good luck.
Simon
