Hello @JordanPhoenix
Go to Administration > Configuration > images and then upload your image with a name and select the file from the icon highlighted on the right side icon.

Then save the images. Logout from the console.
Go to your workflow properties and in the advanced tab select the background imag

Once selected. Logout from your console and go back to your workflow you will see the updated background image.

Let me know if that helps.
Thanks