I think you should try looking for some solid reference of what you want to aim for. Obviously you won't get the exact scene you want but some images with the kind of lighting you want and some with maybe the vibe you want to emulate. Bring those into a pureref board to sit beside your workspace to see what elements you…
well it depends on how big we are speaking. i guess everyone here assumed really big environmental pieces. it is just a matter of texel density or memory usage. a uniquely textured rock will likely eat a lot of texture memory or look very blurry compared to other, smaller elements in the game.
It is hard to tell on that render but there seems to be a bunch of creasing occurring on the front element of the gun with the 5 holes. Or maybe it is just mass out geometry that is faceted.