From my experience with promoters, covers don't really matter all that much. A promotor is after all, only interested in the content of a mix cd. A simple disc image label with your details is suffice (it has to be on the cd, to prevent the details getting confused).
Another small tip is to never include a tracklisting unless it's asked for. Just describe what genre you play, that's enough. Look at it from this direction - a promoter is familiar with all the tracks on your cd, he listens to the first couple of mixes, doesn't think too much of them - your cd is going off. If you don't put a tracklisting, there is a higher chance he is, at the very least, going to skip through the rest of the cd to see where it is going.
Track stoppings are indeed a must, it is rare that a promoter will sit and listen to a full cd, unless you maintain their interest through varied tracks and quick mixes.