I see the same differences in the image you posted as compared to your model.
I know it's near impossible to get the exact same details as the original but at least get the overall characteristics right:
- The hullplates on the original have a larger variation in size than your model, so at least variate it.
-There are some red patches on the body of the millenium falcon in the original
-I saw some laser/phaser -damage on the reference images that would be a nice addition to your model it will break up your model and will add to believeability of your model that it is a war battered smuggler cruiser.
-About the background: it's not that i dislike your background as is, but it just doesn't match up color wise with your milleniumfalcon, I think if you would make a scenery where for instance:
The millenium falcon is going into the atmosphere of a planet, smoke coming from the laserdamage from the hull and somewhere in thecomposition you se a small landingstrip or town.
Something like this will add to believeability and dynamics in your render albeit a lot more work, but I am guessing it's a private project so no rush right?

And last but not least, I am not bashing or trying to put you down I just think giving some constructive critisism has more value than a good job /I love your work and will you marry me ( joke) remarks.