Your colors are marvelous and go so well with the pencils and inks, they look like they were done by the same person.
The addition of rain and the Sentinel definitely make this a more exciting piece. The Sentinel looks a little...fake, like it's not really in the picture. Considering how much shading is on Steven's artwork, I would suggest that future additions like this Sentinel match that kind of cross-hatch shading style. Making its colors darker would help too. The sky and the rain look great though.