when you go to your photos app to view the videos find the video you want long press on it and chose details then on top of this window there is square field for names and stuff so press on it and keyboard will pop out so type whatever name you want in there and press ok

 

uhh but now i see i havent answered your question true all you see are numbers on top. but for me its fine as you still see the preview image of your video

 

If you use Video Player by Jeff Hamilton it lists your video files by name.