Large format gray porcelain would be nice but without anymore info hard to help.I love Mannington Adura Manhattan if you don’t want or can’t have tile it cleans easily does not require new sub floor and looks great. These are both in the gray family .

What are the colours of the vanity and the counter tops? Do you have a vanity or is it a pedestal sink? Anything else in the bathroom other than white tiles on the wall (like wall colour or fixture colours)?

A snick more info is needed. To keep a small space looking larger than it is = white EVERYTHING...but that gets boring.