Seven Kingdoms 2 HD supports up to 1920x1080 screen resolution.
To change the screen resolution, simply click on the current screen resolution indicator at the bottom of the main menu. For example, if the current screen resolution is 1024x768, clicking on [1024x768] will switch to the next higher screen resolution.
Here is a list of resolutions supported: 800x600, 1024x768, 1280x1024, 1600x900, and 1920x1080.