If I, “The Dean," were to be truly helpful, I'd be able to provide you with the percentage of students who submit art portfolios with their Ivy League applications and then I'd also offer you the percentage of those who did who were admitted to their top-choice colleges. But I don't have any of those figures, and I'm not about to pester admission folks just as their crazy “reading season" gets started.
So, for now, all I can say is that submitting an art portfolio is fairly common, and submission alone will not help your application stand out. However, it will underscore your passion for art and is thus very much worth doing. Note, however, that at the vaunted Ivy level, many applicants are very gifted in the fine arts and the competition will be keen. Over three decades, I've seen a few below-average portfolios, many predictable ones (good but not memorable), and some portfolios that have really knocked my socks off. Hopefully, yours will fall into that latter category. If so, this will certainly help your admission odds, although it won't make up for sub-par grades or test scores because there will be plenty of “competitor applicants" who are very talented artistically and who have tip-top grades and test results as well. Your murals may help you stand out the most, but only if they are exclusively—or at least primarily—your own work and were not created by a team.
As you prepare your college applications, try to take advantage of opportunities to have your portfolio professionally evaluated before you submit it. For instance, National Portfolio Day events are free and held across the country. These can provide an excellent opportunity to get your portfolio reviewed by experts while there's still time to improve it. See http://www.portfolioday.net/2014-15-schedule for a list of dates and locations.