VERY small, realistic pixel art

Hi all!

I need a few tips. I’m familiar with pixel art, but so far I only did some cartoon and isometric styles. This time I need to make a realistic piece of pixel art of a forest landscape within about 80x30 pixels.

Can anyone give me tips on what’s the best way to do this?
I’ve got a job depending on this assignment, so any help would be VERY appreciated!

Thanks in advance, guys/girls!

Ferdi