The size is .24 x 24 pixels. That's tiny. And that's the size of your twitter icon that potential followers are seeing. So what does yours look like? Is your logo cut off? Are you using gradients and textures that when reduced are little blurs? A photo of yourself? Make sure your head isn't cut off. An image "borrowed" from another website, photographer or illustrator. Don't get me started on copyright issues. But what I'm saying is to think about it. How others are seeing you. In different mediums. In different environments. Because what you put out there, if you own your own business, represents you. So think about it as the world's tiniest business card. Does it say what you want? Because it needs to say a lot in a little space. Just like a tweet.