You obviously have skills when it comes to modeling and texturing but without the reference picture I don’t think I’d be able to tell what your render was supposed to be.
As Nate said, I think the render is technically quite good. However it’s hard to understand what’s going on.
Perhaps by softening the shadows around the focal point it it would be clearer to see what’s going on. Another idea is to rotate the camera as to see the grave head on, and crop the image a bit.
The objects in this scene look great. However, the background is a little too busy and competes with the focal point in the foreground. I’d probably bump up the DOF a bit or at possibly add some atmospheric haze so that the background is slightly more faded.
In sorting this image out, it might help to consider that the human eye is naturally attracted to the brightest and most-contrasty area of an image, and also that it then seeks to “follow a circular path.” In this case, though, the largest and most noticeable area is dark to the point of serious under-exposure. Meanwhile, the headstone pointing up into it lacks shape-defining shadows and the general 3D illusion.
The eye is then carried to the background(?) architecture, but it is very out-of-focus, and in the intervening space there are no distance-defining cues, which suddenly makes it hard to figure out just how far-away it really is.
Compare this to the natural circular path that your eye follows in the reference pic: headstone, bright area beneath building, dark archway, then an “arrow” of sunlit ground which points(!) your eye straight back to the headstone where it started.
Also use the Histogram tool and compare the shapes of the reference image vs. yours. A good shape is generally bell-shaped sometimes with a spike at either end.
