Did I use this idiom incorrectly?
I'll never forget seeing your beautiful face, but that's just the tip of the iceberg of what makes you a one-of-a-kind beauty.
It's for an English paper. Apparently, it's commonly used when there's a problem, or something negative.
Best Answer
Yes, I'd say it's incorrect.
While it is true to say that, figuratively, the 'tip of the iceberg' is the part of something that can be easily observed while the rest of it is hidden, it is also usually the case that the 'rest of it', which you cannot see, is bad. The tip of an iceberg typically signals a menacing monstrosity below.
Something of which the greater part is unknown or unrecognized. Chiefly in the tip of the (also an) iceberg: the smaller, perceptible part of something (esp. a difficulty) which is evidently much larger (OED).
The problems that you see here now are just the tip of the iceberg. There are numerous disasters waiting to happen.(http://idioms.thefreedictionary.com/tip+of+the+iceberg)
a small, noticeable part of a problem, the total size of which is really much greater - http://dictionary.cambridge.org/dictionary/english/tip-of-the-iceberg
This is only the tip of the iceberg. Our problems can become much worse. https://en.wiktionary.org/wiki/tip_of_the_iceberg
The phrase “tip of the iceberg” is used to refer to a situation in which you or someone else is seeing only a small part of what is really a bigger problem. So, the iceberg is used to refer to the fact that there is a very big problem, and the “tip” is a small part of that iceberg, or a small part of the bigger problem. The phrase has a negative meaning to it – and is usually used to describe situations or people that are difficult.http://www.programmerinterview.com/index.php/american-vocabulary/what-does-tip-of-the-iceberg-mean/
that phrase usually means that there's a lot worse beneath the surface or that you don't know about...https://uk.answers.yahoo.com/question/index?qid=20090508141814AAQ9WEu
a problem or difficult situation that shows that a much more serious problem exists http://www.macmillandictionary.com/dictionary/british/just-the-tip-of-the-iceberg