A Broken Mirror
There are many interpretations of what the Malkavain Clan Symbol, a "Broken Mirror," actually means. This perfect little metaphor does a lot to explain Malkavian philosophy and from several different angles. Here are just a few.
The Obvious Answer
You are broken. The way you see the world is not right. Normally, a mirror gives back exactly what it is given, it understands. You are mad, you do not give back correctly. Something is wrong with you, you do not understand.
From this perspective we are using several allegorical references and few assumptions. The idea that the mirror represents perception is common through most interpretations. The ideal of the mirror is that it is perfectly truthful. Think of Snow White, the Queen's mirror was a source of great insight and truth. How many movies show the lead character talking to himself in a mirror as he uncovers "the great truths" of his life? The fractures are a flaw. Simple enough.
Now Turn it Around
Why does this mirror have to be you? No, reality is broken. All the mirror can do is show you what's out there, and what's out there is flawed! You are the truth, everything else is broken.
Mirrors reflect, so reversing the frame of reference like this is entirely plausible. Go through the looking glass and look back. Does reality create the reflection or vice versa?
Or maybe...
...maybe you are the mirror. You are not truth, you are its reflection. You show the world precisely what it is, what it doesn't want to believe is true. You point out every flaw, you point out every crack. You are a constant reminder of what everyone wishes were a lie. You are proof of just how fragile the mind is.
Madness is a frightening thing to behold, doubly so when it is your own. This is one of the major purposes behind pranking, not to drive people mad, but to show them that they already are. I am the mirror, do you like what you see?
But what am I looking at?
Still others say that it isn't a broken mirror at all. The insist that it is a bolt of lightning reflected in a perfectly smooth looking glass. Lightning is a symbol of power, and a herald of change. The same arguments as above hold for where that power is. Are you just watching? Or are you the source?
Metaphor within metaphor, it's hard to argue that anything could be more appropriate.