Variety will save your ass
Arguably the most important part of your application is your portfolio. Your work will be scrutinized, mulled over and compared to thousands of others. One of the most important things to remember, and the easiest to forget, is that your portfolio has a much higher chance of getting you in if you focus on the work as a group, and don't think of your pieces individually. RISD doesn't care if you can photorealistically render twelve portraits. What they're looking for isn't technical perfection (that can be drilled in later) but rather a willingness to experiment and mess with expectations.
I'm confident the only reason I was admitted was variety: I submitted a collection of mediocre paintings, drawings, photography, animation, design, typography, digital illustration, building models, and shoes made of trash. If I had submitted 15 photos or illustrations of average quality, I doubt I'd be where I am today.