What is the perception of students who take a gap year between their graduation and starting graduate school?
When I was looking into this for a former student of mine I spoke with the head of the graduate program at the US Top 20 program I was working in at the time. He actually viewed a gap year as a good thing. His rationale was that students who had held jobs and managed to live for the gap year were more likely to have the work habits useful in graduate school. 

When it comes time to write your applications you just have to remember to explain how that year has made you a better candidate for their program. It might not be more math that you've learned by it may be maturity and a renewed sense of purpose. If you chose to take a year off do something worthwhile and don't just study for exams.