Did you know that CSS3 has a style called
shape-outline? It’s pretty neat, it makes it so that a floated object gets a shape based on the alpha channel of its specified image. But it’s kind of a pain to set up; in plain HTML it looks something like this:
<img src="/path/to/image.png" width="320" height="320" style="shape-outline:url('/path/to/image.png');float: left">
and if you want a different shape mask for your image than its own alpha channel, you have to do a bunch of stuff like making sure that the image sizes are the same and whatever.