There are a plethora of web apps for content creation available. There are also a variety of image editing & drawing apps in the Chrome Store (and a basic drawing app in GApps).
Edit: If you want iMovie, you want a Mac. My family doesn't use iMovie (though I do personally, but the ChromeBook isnt't for me), they use YouTube video tools & Facebook video crap.
iMovie (which was the example you gave before you edited your comment) is way, way too complex for my family members, from experience (and even me, at times).
I'm helping an old lady in my neighborhood edit movies of her kindegarten class in iMovie, and I'd bet that most people would have said "oh, she doesn't need to edit videos", but one of her colleagues starting making montage videos of the class for the end of the year and she wanted to do it too. Since she has a MacBook, this is possible. If she had a Chromebook, she'd have to borrow someone's computer, and I don't know if she would have the courage to ask for that, especially since, like most old ladies, she is scared that she will break computer every time she does anything.