If this occours as part of labeling the images naturaly, I suspect you'll avoid penalisation (but I wouldn't expect you to get a bonus for MINKW, you might for the long tail however)

Generaly, I would be carful using alt tags for pure SEO benifit. They are there to help with accessability, and you risk losing that if your alt doesn't describe you image. (or at least most of them)