(What is / How do I change) the icon next to my (Organization / User)?

It is a gravatar.

If you have not signed up for one we will display a randomly generated one for you. Once you've created one we will use it in several places.

You can get a gravatar here. https://en.gravatar.com/site/signup/ Please use the same email you signed up for Hospitium with.

To change the Organization gravatar, set your Organization email by editing you current Organization.

You can find out more about editing an Organization here.