https://discuss.asciidoctor.org/Ongoing-effort-for-LibreOffice-Packt-backend-tp1823p1826.html
The problem you are having with the image attributes is due to not using the correct inline syntax.
I recommend looking at the slim docbook backend when you get stuck.
If you just want the path in the attribute, then you'd type:
xlink:href=image_uri(attr :target)
If you need to surround the path with round brackets (if I understand what you are doing correctly, you need to use interpolation).
xlink:href="(#{image_uri(attr :target)})"
That should get images to work. The image_uri function handles all aspects of resolving the path to the image, taking into account the imagesdir and data-uri embedding.
NOTE: The target for block images is (oddly) stored in the target attribute, not the node's target property. Inline images store the target in the target property. In the future, I may align these.
-Dan