As far as I know, there is not a way to remove the Name at the bottom. For a partial work-around, Players can change their display name within a game (it will not affect their Roll20 name, nor their character name, just their display name in the game along the bottom). You could ask all the Players to change their display to "A" or their initials, or a tiny punctuation mark. This will let you fit very-many names side by side, before it fills the space. Perhaps you could ask the Players to keep their name displayed, but Observers must change their display name to "O". I am curious, how many players and observers do you have, that it fills the area?