Like an introduction to a book, your statement presents the fundamental underpinnings of your art; write it for people who like what they see and want to know more, not those who already know you and everything your art is about. In three to five paragraphs of three to five sentences each, provide basic information like WHY YOU MAKE YOUR ART, WHAT INSPIRES YOU TO MAKE IT, WHAT IT SIGNIFIES OR REPRESENTS, WHAT'S UNIQUE OR SPECIAL ABOUT HOW YOU MAKE IT, and briefly, WHAT IT MEANS TO YOU. Don't bog readers down, but rather entice them to want to know more. As with any good first impression, your statement should hook and invite further inquiry, like a really good story is about to unfold. Give too little, not too much.
People have short attention spans. When you overload readers with details, you risk drowning them in minutia, and discouraging those who might otherwise persevere if you keep it simple. Address and answer commonly asked questions about your art. Save the complicated stuff for those who progress to the next level. Don't worry about having to satisfy your dedicated fans. You won't bore them and you won't lose them; they already love you. And if they have questions, they know how to get them answered. Remember-- your statement is about broadening your audience, not keeping it static. You'll have plenty of time to give your most recent converts the grand tour-- LATER, NOT NOW-- you have to convert them first.
Plus this... your statement is about you, so personalize it. Write it in the first person, not like you're talking about yourself in the abstract. Infuse it with your unique perspective. Whenever possible, make it conversational, like you're speaking directly to readers (note: a good editor can work wonders here). The more complicated, theoretical, arcane, inscrutable, bloated, pompous, elitist, egotistical, bombastic, arrogant or impersonal your statement, the more trouble people will have trying to hack through it and connecting with you and your art on meaningful levels. Few readers want to burn calories trying to decipher complexities; they burn 'em all day long. For now, they just want to see your art, take it easy, have fun and enjoy themselves.
Additional considerations: