Here's how crazy I am:
Making the cover is the second step in the process of writing a book for me, after blocking out the storyline and selecting a title, because whoever is on the cover has to BE IN THE STORY. Furthermore, whatever they're doing has to be relevant to something they do in the story. Since I mostly use stock-ish images of women in not highly recognizable situations, this isn't as hard as it might be, but if they're doing something with their clothes or they have a certain expression or whatever, it has to be in the story. I can not have a story whose cover image doesn't relate to something that happens during the story. (This is one reason I'm trying to learn Poser.)
The story I started today, A Matter of Trust, has a male character (of course.) I now know what he looks like, because I licensed a stock photo with a couple in it. He looks like the man in the photograph! I wouldn't have picked the photo if I couldn't work with it at all, but it certainly solidified his appearance. (And also inspired a minor plot point having to do with how relatively young he looks.) Furthermore, the person has to be a significant character, and preferably appear early in the story. The person on the cover of At His Discretion is the second woman (Ekaterina) who appears in the story, not the first, and believe it or not, that bugs me a little, but the picture was so hot that I just couldn't resist it. :) The second woman who appears in Maestro (Maya) is also the character on the cover of that book, but that one I commissioned and none of the blonde models showed up, so it wasn't for lack of trying.
I'm also using a pretty graphic image on this new one (no actual naughty bits visible thanks to some Photoshopping - some sites won't post graphic covers) as the overwhelming consensus is that the nudier your cover, the better it sells. But I personally don't care whether a cover image isn't all that graphic... this is the other side of my insanity: I try to guess what the story is like based on the cover. I love the cover of At His Discretion even though all you can see is a little bit of bra, because to me it's all about the expression and the pose.
So, if you wondered, that's why Unspeakable Publishing publications have the highest standards of integrity when it comes to what-you-see-is-what-you-get. Because I'm nuts.