Sometimes the cover is the best part of a sketch book and in this case it was the only part.
Ideas don't always come as easy, I find putting pen to paper or hand to mouse and letting your mind roam free is a great way to get ideas flowing.
Experimenting and not trying too hard to get the finished product can give you just as many good ideas. I try to be different in my approaches to see what I come up with.
Of course it might not always work out as expected but the next doodle or sketch might be the idea that is worth pursuing.