Currently, Diablo II will not run fullscreen on a Mac in CrossOver. Fortunately, there's a simple fix to get your hack-n-slash on.
Under the Programs menu, select Run Command…
In the new dialog that pops up, select your preferred bottle and click Browse…
Find your Diablo II.exe file and select Choose.
Add -w to the end of the path, so that your path looks like this (my Diablo II installation is stored inside my bottle, but the exact path to your app may vary -- just focus on adding the -w to the end of the path):
"/Users/username/Library/Application Support/CrossOver/Bottles/Diablo II/drive_c/Program Files/Diablo II/Diablo II.exe -w"
The quotes are there to begin with and need to remain. Do not delete them.
You're now ready to run your game. To avoid having to do this every time, I suggest clicking the Save Command to Programs Menu button. This way, you can simply choose Diablo II from the Programs menu and it will automatically load in Windowed mode.
Enjoy!
