I came up with an idea, I doubt I am the first to have it but still, about shading. While it would be a lot more work, would making shading an overlay be worth the visual bonus if it was done right?

An example of what I mean would be, say a game had a day and night system. Would it be more visually pleasing to have shading on a mob be created by an opaque layer, that is changed based on the time of day or the type of lighting. So, a lighter, opaque layer that is accurately placed over an icon during the day-time would be used to project that the sun is what is shining on them. The general icon would be lighter, and have a stronger glare than a night-time overlay, while the night-time overlay would give the entire icon a darker appearance and less glare.

Just wanted an opinion on whether or not it would be worth the extra work to get the visual bonus.
I like the sound of the daytime, but whether it'd be worth the work or not is up to you. The nighttime shading is kind of already done by the dark overlay over the player's screen. To test it you could have two pics of the icon and add the sun glare, does it add depth?
Well, thinking more about it, it would be a lot of work to do shading in that way. Considering you would have to do it for most, if not all objects as well. I just got to thinking that it would also be a good addition if you wanted to, another example, change the location of the sun or moon. So the lighting would be changing angles to give it more of a "real" feel rather than always being at the same angle. Because the sun isn't always in the east, it moves throughout the day and so on.