Disk images (DMG files) are a little annoying. You have to mount them, run an installer and then get rid of the mounted drive and remember to clean up the related DMG file.
Not any more: DMG Cleaner is a helpful little tool that makes it easy to keep things tidy.

This is how it works: Keep DMG Cleaner in your dock or as a shortcut on your desktop. Then, whenever you have a disk image you don't need any more, simply drag the mounted disk image onto the icon. The app will then launch, unmount the disk image, find the corresponding DMG file and move it to the trash. (Alternatively, you can also drag the DMG file onto the icon.) After finishing its work, the app will automatically close. That's it!