Image Sizes

Hero
1500x580px
The hero is used on the home page and section pages. But you can use them on any content page as you see fit.
home
section page

Icons Sizes
80x80px
These are shown in cards and in the home page modals.
home

Panel with Caption
1500x1000px
Example of these

Testimonial Image
750x670px
Testimonial Panel Examples

Article Thumbnail
640x360px (Optimal Size)
Any size will display within the box
Article thumbs are used on article list pages

Article Heading
1460x420px
Can be any height you choose
Article heading example

Side Content Image
250x350px
Add .image_normal as a class in the source code for side content you don't want to be 100% width.
Side content normal width image example