If you upload an image on the Build plan, you can see the compressed version. This is served compressed to ensure the best page load speed when loading this image into your page.
Image quality settings
On the Measure (Optimize for Magento) and higher plans, you can choose the image quality level that is served on your site.
If you are familiar with Photoshop's Save for Web feature, the Build images could be compared to saving for web at 80%. The Measure and above plan images can be compared to saving as a standard jpeg at Maximum quality, if you so choose.
These images focus on quality over file size. They are most beneficial and noticeable to users on high definition/retina displays.
Custom Elements
You can also make a Custom Element to host your own images
Open the Custom Element Editor
Add this code: <img src="{{ image_url }}" alt="{{ alt_text }}" />
You'll notice that when you paste that into the template editor in shogun, a menu appears on the right letting you configure the variables
Change them so that they get entered on the Sidebar rather than inline
Save your page
Then you can go into the editor and your custom element can be seen from the sidebar.