The user upload option for ZIP files is useful if you have quite a few students and would like to upload the images all at once. This is the only option to upload a ZIP file, but there are other places you can upload images:
If you’re looking to add logos for the Departments page, you could upload these through School Admin > Manage Departments. There’s a logo upload option here where you can upload an image from your computer.
In Planner > Manage Resource, you can upload images as a resource and make these available to lesson plans. These can be added or inserted anywhere you see a Shared Resources option in the rich-text editor, such as unit and lesson plans:
Hope this helps! Feel free to share a screenshot if you have a specific use in mind.