This is intended. When multiple pictures are provided the script will only pick a single image. The reason behind this is you can only attach a single image and a single thumbnail in a single embed. The thumbnail is not used in my script.
I could post the picture in multiple messages or multiple embeds but it looks bad. If you want it I can point you in the right direction but I won't add it to my script.
This is outside of my control. The tweet on Twitter has a picture. My script retrieves the data through the Twitter API. This is what my bot sees. The image link is not in the json. I don't know why for some tweets Twitter chooses not to include the picture hyperlink but since they are not providing it through the API I can't access it thus I can't post it to Discord.