This is just reference information (not a complete answer).
My EQF plugin may help for you. however, because this plugin shows attachment file to only question page, remodeling will be necessary. In addition, if you display image in question list with this plugin, display performance of question list will deteriorate because many queries are executed for getting extra data. It is necessary to remodel the query of a core acquiring a list of questions to prevent deterioration of the performance. It is difficult. There will be another method to extract first image tag from question detail with regular expression. But, this method is not user-friendly.