It's up to you to add a label string to the image morph. One way to customize this particular implementation is to replace the images that are used for the check box with other images, to fancy it up a bit. Pretty standard stuff, that's the way the Linux guys fancy up their check boxes, and we already have a good handle on how to do this ourselves. But you know us, never do something easy when you could just as easily obfuscate a nice implementation. Rather than just do the simple and obvious, we're going to make some engineering decisions and have a little bit of fun.
Most operating systems are pretty strict with how their controls look.
Usually there is some standard look for the check box, along with standard fonts for the control labels. That provides for consistency across different applications. I've found it is much easier to come up with a catchy slogan than to actually write code, and a good slogan can get you out of doing a lot of busy work, believe me. It's much easier that way, and you don't have to listen to all those silly people who have nothing better to do all day than sit around making sure that your product complies with ISO something something or other. Well standards guys are the same way too.