Hello,
UPDATE: latest versions of phpdocx support adding WordFragments as table and list values when doing replacements.
Using the current version of phpdocx, the best approach is to do this task in two steps:
1. Add placeholders as values.
2. Use the method replaceVariableByWordFragment to replace the previous placeholders to add the images.
We're working on adding WordFragments support as values in list and table replace methods.
Regards.