It still looks very cut out in places, plus you have no real contrast on anything. Lighten your lights and darker your darks.
Those yellow areas I'm assuming is supposed to be light but it isn't reading well, I think either remove them or get some reference.
Also, whats the story behind the illustration? Why is Grim standing in front of a cut out of africa filled with happy children? If it's a comment of the high death rates and diseases and stuff, then I suggest using a different image. Maybe some starving/ill children, instead of well dressed happy ones.
I have a bad tendency of drawing out of my head all the time...
Depending on what I'm drawing I also do that.
I just put the pictures up so you could see what a skull with cloth on it would look like.
When I draw from imagination I try to keep in mind what I'm drawing.
And what it would look like.
For example, take the robe you drew. It's not made of concrete so gravity will pull it down. It will move straight down except when blocked by something.
When it's blocked with a lot of it hanging below it, it will make sharp lines, when it's blocked with little hanging below it, it will fold and bend more.
But when I'm not sure I just experiment with stuff I have at hands.
Furtermore, and I forgot that in my last comment, I think you might want to work on what you are trying to express.
Danlambert was right on that, happy (African) faces with the grim reaper in front of it doesn't really match.
It could be that this is what you represent, that happy African children can can die any moment. So perhaps you could tell us a little about that so we can focus on that at first instead of going straight to the details of how to make a better grim?