MiniDLNA works without problem for my Samsung TV, until I add thumbnails.
When I add them, I see the thumbnails on the (samsung) TV! but... then the videos don't play anymore. It seems then minidlna serves for the video the image/jpeg mimetype!
can also confirm this using the DK Dlna DLNA client on my android smartphone: the video plays fine until I add a thumbnail. Then when clicking the video, it asks whether to open it with the gallery or image viewer and says it's image/jpeg.
Also others have seen this problem:
I found that the change i attach (against 1.0.24) fixes the problem for me.
Sadly it fixes it for the TV, not for the android software. For the android software I found that commenting completely the "video" handling of album art and keeping only the "audio" part makes it work perfectly...