You can now add category images which will show on the relevant category page and associated buttons (if your theme allows). This is as simple as adding an image to a product:
Adding Category Images
Click to Edit the relevant Category.
Scroll down to the Category Image Panel.
Click Image Manager.
Then Select or Upload the relevant Image.
Click Save and you're good to go.
Displaying Category Images on Shop Front
Head to the Shop Editor and change the page preview from Home to Category (Standard).
Click the cog symbol when hovering over the content block.
Toggle on the Cat Header Image option for the image to appear on the category page.
Hit Save and make sure to Publish Live.