Hi Emmanuel,
It happens, because Taxonomy Terms does not have images in WordPress by default, only descriptions: https://i.imgur.com/Avf2mTb.png
Because of that, there is no unified API to request the image. The description should show up when defined though.
Some of the taxonomy image solutions are integrated to the plugin, such as the WooCommerce product category images or the Categories Images plugin, those should work.
Let me know if you use a different plugin, or any different method to attach images to the taxonomy terms, and I will try to construct a custom hook/function to somehow parse those images.