This is my first custom built module ever. It is a hero bar, where the only thing the user has to do is to choose an image. On top of the image you can e.g. have text with Call-to-action buttons, forms etc.
I often stumble upon this problem where I need a background image behind some text or a form. It is easy to solve it with one image declaring it directly in the CSS code, but then the customer can't change the image. Of course you could use the image module, but then you have to write a lot of code in order to get it to work properly. This is simple, easy and useful!