I don't have time to write a dozen pages on specific mistakes, sorry. :/
I can mention a few. There is inconsistent lighting on different parts of the picture: you have an elephant lit from top-right (except for its ear), an elephant lit from the front, and riders lit mostly from top-right, but not all of them. You have spurious tangents everywhere, the rider's head coincident with an elephant's leg, a notch in its ear coincident with the howdah, a pike coincident with the blanket, and I suspect I could fill a page just enumerating those. You have a problem keeping parallel lines parallel and ellipses round. Your values are inconsistent: horses in the open are several grades darker than the windows of a building. You gloss over anatomy where you aren't sure of it. You are using neutral grays for shading. Most of your edges are scribbly or dirty, and overall your brushwork is very sloppy. The detail level is not used well; you have the same level of detail in the background figures as the foreground, instead of using it to emphasize the point of the picture. And so on, and so on.
This all boils down to a need for overall skill improvement, not to a few changes you could make to fix this picture.