How to get rid of white space around embedded images

There are at least three workarounds, maybe more:

1. You can reduce (but not entirely eliminate) spacing by right-clicking on the topic and going to Format Topic. In the "Alignment and Images" tab you can set the image padding to 0mm. In the "Size and Margins" tab you can set the topic margins to 0mm. This will still leave a small amount of spacing around the image.
2. As 1, change the topic shape to "No line", and make sure that the topic fill colour is the same as the map background.
3. Use a background object image instead of a floating topic.