I am not sure, couldn't find a solution - so i think its not possible yet.
Please add function to embedd preview pictures to the idml-file.

Our need: For distribution to an translation office, we send the idml-file PLUS an PDF to show what the the idml is showing.
I know - with every more picture info the size is increasing, but with an option to choose "show preview picture in idml" it would be phenomenal.
All info text+pic in one file would help the recipient to the see the same as you.

Pictures are mandatory for translation office, as they need to see what you are describing.