WHAT MAKES A GOOD CD/DVD COVER?
It should be instantly recognizable in some way. Being dramatic helps. A band or label would want their product to stand out and be visually distinct on a shelf full of other albums. This means that it should ideally have a single, well defined subject or point of focus which stands out strongly and decisively. It makes it easier to lock onto.It should also ideally tell a story which somehow folds in with the either the band or the actual music. That leaves the door open to a lot of possibilities, but it does mean that the photo can't be too vague, or just have random things on it, or require too much thinking to figure out.
Also, an album cover is not just a product shot, or something which gets put on an album just because an album needs to have an image on it. Some famous covers had no image at all. No, a cover should enhance or "color" the music somehow. It needs to add something to the overall experience, not distract from it.