Tversity Custom Thumbnails?

Hi all not sure if this should go in this forum or the PS3 forum as it kinda pertains to both. But was wondering how I can setup custom thumbnails for movies on my Tversity server. Tversity seems to auto generate thumbnails from avi movies, like the first frame which is pointless. It puts the jpeg image in /user/appdata/local/tversity/data folder. I found I can make custom thumbnails if I find the movie in that folder and modify the jpeg. However this is very tedious and can take me months to modify all the movies I have. Also Tversity doesn't even attempt to create thumbnails for VOB or some other video formats which is what I would like it to do. Is there an xml file somewhere I can change so it does? Or any other way to make this process easier?