Own poster from own video

Hi,
If I want to consume media with Kodi, I have to decide wether this is a picture, a song or a video. The program can play all sorts of media, so I don’t understand why it is necessary to make this decision first.
So, if I want to see a poster of a selfemade video I have to put the photo in the video folder and choose „picture“. Then I can watch the photo AND the video. But if I choose „video“ in Kodi and open the video-folder I can’t see the poster, which makes no sense to me. It would be much more convenient to browse through folders and to be able to see the contents – no matter if this is a picture, a song or a video. Or is there a setting to do so already?
Thanks!