I'm kind of curious how people feel about this one.
VN protagonists tend to be rather obscured. Rarely are they voiced and rarely do you see them, and half the time when you see them, you don't see their faces. I assume this is mostly for immersion value, so that the player feels he's in the role of the protagonist... which is a valid concept, just not one that fits my reading/playstyle.
I like having a clear picture of the protagonist with a good voice actor, since I rarely feel I really identify with the leads. Since the lead isn't "me" in my head, I like him to be as fleshed out as possible. I do feel that having sprites for the lead is a little excessive though, and the only time I've seen it done was in the x-change series, where it kind of worked because the protagonist also the main sex object.
Example: One of my favorite CGs that I can think of is the fist bump scene from princess waltz, IMO it adds a lot to clearly see the protagonist and his body language when interacting with other characters.