Great photography makes the subject stand out. One ways of doing this is by keeping your subject in color, and changing your background to black & white.
Thanks to the PhotoRoom cut out feature, this is simple to do. Here's how:
Tap the + button to "start with a photo"
Select a photo
Tap the "black and white" background in the "Classic" templates
Export the photo
You can fine tune this effect by doing the following on the background:
Tap Background then filters and select another black & white filter
Tap Background and adjust to decrease the background contrast
You can also fine tune this effect by doing the following on the subject:
Tap object/person then adjust, to increase the saturation and contrast