pglombardo: This is an older thread but I got Stronghold to run in windowed mode on a Mac with the following steps. Hopefully this will help other Mac users.

Open a terminal window and change to the root user by using 'sudo bash'. It will prompt you for your password.

Change directory to '/Applications/Stronghold HD EN.app' and open the Wineskin config utility with 'open Wineskin.app'.

Here are the list of commands to run in Terminal outlined so far:

sudo bash
[enter your password]
cd /Applications/Stronghold\ HD\ EN.app/
open Wineskin.app

This opens the Wineskin config utility. (see screenshots)

Click "Set Screen Options" - this will bring up another dialog.

In that new dialog, select "Virtual Desktop" and select your desired resolution - see screenshot attached.

Click 'Done' and you can test your config by clicking 'Test Run'.

Exit out of the config utility and now you have StrongHold running in Windowed mode.

01kipper: An easier way to open the Wineskin config utility is to hold down the Option key while double-clicking the game app :). (Works for all Wineskin games).

(You can also right-click the game app and select "Show package contents" then double-click the Wineskin app if you prefer.)