Pretty good drawings you have.
The grave looks shiny because the shading is sudden.
Its still a nice drawing though, I'll give you that. It actually looks pretty cool. My only suggestion is to triple up the text layer and have one a silhouette, the other white, and the middle the color of the object. You move the white to where the light will hit it, then the silhouette to the opposite side, middle stays the same. This will cause it to look like it sinks in.
Either way, cool stuff, you are pretty good at concept.
Attached is an example. Its only an example of what I suggest you do to your drawing, so its shaded in a similar style.
Edit: attachment removed now that OP has seen the example.