You can force video settings via command-line parameters.
Try these settings:
-width 1024 -height 768 -fullscreen 1
For the linux build I think you can add these parameters to the end of the last line in the atomzombiesmasher run script file (the file you click to run the game).
All the command line parameters can be found here- http://blendogames.com/atomzombiesmashe ... tm#command