I know this is an old post, but since it has been unanswered I'll take a shot at it, based on what I've heard from several MBA applicants we've helped get into Kellogg.
Before that let's broaden the scope of the question, so it can benefit others who aiming for M7/T10/T25 schools and not specifically Kellogg.
The culture at any MBA program is a function of several parameters - people would be right there at the top, but there's also location (campus vs city), academic policies (grade non-disclosure), weather (sunny vs wet/cold).
A lot of what you do during academics and outside would influence your overall experience.
But it comes back to the first one I mentioned - people.
B-schools have a stereotypes assigned to them - down-to-earth vs arrogant, collaborative vs competitive, academically-focused vs not.
Many attending Kellogg have said they found the culture to be very friendly and collaborative. The people are comparatively easy-going and humble, compared to several other schools in the same league.
In fact, a lot of academic work you do at Kellogg will be team-based. So you have no option but to learn to get along with others.
Having said that, even after you start and complete your MBA, your definition of the school's culture may not match another classmates'.
Why?
Because humans have a tendency to form cliques. You'll gravitate towards the groups that are aligned with your personality and interests.
For all you know, the impression you've built after interacting with a smaller sample of students/alumni could change drastically once you start the program.
So I'd say, don't try too hard to put a label on the school culture. Go in with an open mind. You'll find your tribe soon.