Hey.

I got a new monitor which is 1080p, but 1080p seems to look bad on cortex command as the background is black at some parts. Is there any way to fix this?

What are your current view settings?
I've found it looks ok if you make sure you have either the exact same resolution as the monitor, or exactly half, scaled in CC (rather than by the monitor).

However, given that CC is not really intended to be played on a huge screen (all weapons snipe, backgrounds vanish, etc), you might never get the sort of gameplay performance from a large monitor.
Oh, and small levels are really weird sometimes.

if I am mistaken I'd love correction; I too have a large screen that I never use due to general lameness of massive scaling issues and the game-breaking long viewing range.
As there's no fog of war (yet!), I do not think those things are fixable.

Iirc, the background letterboxing or w/e you call it can be fixed by making bigger background images, but I could be wrong.

But yes, at the base of the problem is the fact that Data never really meant the game to be played in resolutions much higher than 640x480, so already you're into unsupported territory.