Beige carpet,black furniture what color walls do you suggest?

Soft blues and greens are very pretty.

Check out this chart (copy and paste in your browser): http://www.nonslipindustrialflooring.com.au/wp-content/uploads/2015/11/as2700-grey.gif

It has options for wall colors with both the beige and black. Personally, I would go with a gray shade. Good luck!

Cream.

off white, or maybe cream

I have beige carpet and black furniture in the master bedroom. I chose a lilac color for the walls. I have had so many compliments on that room...and I still love it after 7 years. Think about your favorite color and go for it.

https://www.homedit.com/color-that-work-well-in-combination-with-black-furniture/

Go to the store and get some paint chips/sample of color and take them home. Hold them up to the furniture, walls, etc. and see what looks the best and you like the most. I did that and found that a certain shade of green was better to go with my wall color and counter tops instead of plain white on my kitchen cupboards.