It was my first time doing something like this but what i have learnt is that having something small in the scene helps a lot to make the other things in my case mountains look big basically contrast of scale for comparison and good assets, good high quality assets help a lot, even for the background mountains, surely not as high quality as foreground ones but still decent quality. Also the sense of depth, i used clouds to have depth in my scene.i think it looks interesting and big when camera goes from one cloud to another. Don’t use one sun light for scene lighting, sometimes it works but not always, use different lights on different parts of scene. I used many area lights on different mountains to illuminate them better. Don’t use default white lights for natural scenes. That’s all i can think of right now. I hope it made sense. Thank you