Image sizes can be set when you first add the image in your page. The size can also be changes by right click on the image-> image properties.

Here is the example of the image sizes: 

Image Type Size (width by height)
 Page Using Image Type
Banner Image Preferred Width 1920 pixels Academics
Center Column Image Max Width 434 pixels Residence Life
Right Column Image Preferred Width 276 pixels Admissions & Aid