Cover models

They say you aren't supposed to judge a book by its cover, but I often find myself doing just that. If there's a model on the cover I usually picture the main character in that book to look like the cover model. Today I got the cover for Hair of The Wolf, which included a cover model. I was a bit shocked at her appearance and my eyes lingered on the cover for awhile. It took me a minute to figure out what was wrong, I had pictured her differently. I had pictured Anyssa to have soft features, like a slightly chubby face that was friendly. I realize that when I read a book I may not be picturing the character the same way as the author did, but now I find myself wondering if the author is always happy with their model. I know that traditionally published authors have no control over their covers, but what about self published authors? I would like to hear more from people about their experiences with book covers and cover models. Did the cover always turn out as expected?