What do Ivy League schools look for in an applicant other than grades or test scores?
While grades and test scores are important, colleges take many other factors into account. Essays, awards, arts supplements, positive teacher recommendations, extracurriculars, work experience, and summer activities are all important parts of your college essays that should not be overlooked. Qualities that admissions officers look for include intellectual curiosity, initiative, thoughtfulness, and leadership. When applying to top-tier schools, a stellar transcript is by no means a guarantee of admission. But by the same token, this "holistic" admissions process also ensures that a few academic slip-ups don't bar the way for an otherwise superbly qualified student.
In general, top-tier schools are looking to put together a well-rounded class with a diversity of passions, talents, perspectives, and interests. Typically, admits fall into two categories: "well rounded" and "well lopsided." "Well lopsided" students are those who found their passion early on and have demonstrated their interest by hard work and, subsequently, success in whatever particular field they enjoy, whether that be biology or bee-keeping. Still others are "well rounded," meaning that they find interest in many different areas and have cultivated their interests to excel in many different fields.
Is it risky to send in a creative writing supplement as part of my application? Since the faculty, as opposed to the admissions officers, will read my submission, will it be held to higher standards?
Typically, college essays are, in fact, read by people who are part of the admissions committee. Creative writing or arts supplements, however, may be read by either faculty members or members of the admissions committee. Who reads them depends on each school, and it might be best to ask the school you are planning on applying to what their policy is. Supplements are held to no higher standards than the application essay. Sending in a creative supplement signals that you are, perhaps, also interested in joining a particular group or club, or are enthusiastic about getting involved with the artistic opportunities at a college.
That being said, submit a creative application only if you truly think your application will benefit from a sample of your creative work, and don't just do it for the sake of sending in something else. Wasting an admissions officer's time by giving them things to read that don't add anything new to the picture is never a good idea. These supplements are meant to show a side of you that you might not necessarily have been able to show in your common app essays. So if you're serious about creative writing and you think you have some quality work to send (the shorter the better), go for it, but think twice about sending in work just for the sake of sending it in.
If I have a mental illness, how should I factor that in when deciding what schools to apply to?
It is strongly recommended that you check to see what mental health resources are offered at the colleges to which you want to apply. Mental health resources can vary vastly from school to school, and it would be advisable to research the colleges on your list if you're concerned, just to know if you'll feel safe at the place or not. A good resource to check out is the National Alliance on Mental Illness.