Are you asking how to do this through the Discussions API, or how to do this through the regular interface?

The discussions API, I don't think you can combine poll and text through the regular interface.

True. I managed to do it with the following JSON payload:

{
    "body": "Asd asd asd",
    "forumId": "1352818",
    "siteId": "1352818",
    "title": "Asd",
    "source": "DESKTOP_WEB_FEPO",
    "funnel": "POLL",
    "poll": {
        "question": "Asd",
        "answers": [
            {
                "text": "Asd",
                "position": 0,
                "image": {
                    "url": "https://static.wikia.nocookie.net/520439ba-6c26-4e04-a9e5-3e4ecabe61bc",
                    "width": 112,
                    "height": 112,
                    "mediaType": "image/webp"
                }
            },
            {
                "text": "Asd",
                "position": 1,
                "image": {
                    "url": "https://static.wikia.nocookie.net/2099e3ff-751d-466b-a53d-4270d582ecb9",
                    "width": 112,
                    "height": 112,
                    "mediaType": "image/webp"
                }
            }
        ]
    },
    "articleIds": []
}

and the request was made to /wikia.php?controller=DiscussionThread&method=create&forumId=1352818. The images were previously uploaded through /wikia.php?controller=DiscussionImages&method=uploadImage, by passing it a FormData payload (the MIME type is multipart/form-data) whose data field is the image data and whose context field is set to discussions. Is this the result you wanted to achieve?