Straight male. Great face, average body.
About someone in particular? Rarely happens, but in this case I certainly always have her face in mind. Actually, when I think about it, it’s the only part of the body I’ve clearly in mind, the rest being a rather blurry concept (which isn’t surprising since in this case, I normally don’t know what the body looks like exactly. If I know it, I probably don’t have to masturbate anymore).
When it’s not about a particular person, they’ve normally a perfect everything, anyway, and the situation is perfectly ideal too, so it doesn’t apply. And situation, words play a more important part in these fantasies. Once again, the physical appearance is a rather blurry and changing concept (doesn’t mean that when actual intercourse is involved, the physical appearance plays a similarily minor role).
When I think about it, “what exactly do you have in mind when you masturbate?” (not “what fantaisies”, or “what kind of people”, but rather "are you fantasies situationnal or much more visual, do words play a part, do you have a clear mental image of the “partners”, do you fantasize about specific persons, etc…) would be an interesting IMHO question.
No to the first question. But I wouldn’t use a picture only depicting, say, breasts, either. And given the choice between both, I’d go for the face pictures.
I rarely pleasure myself to a picture anyway, prefering my imagination. But in this case, the face (and also, quite important too, facial expression) is most certainly my main criterion to pick some girl’s picture over another. All have great bodies and great faces anyway so the choice is rather between “stunning faces and great bodies” and “beautiful faces and stunning bodies”.
Of course, a nude (or scandily dresed, depening on the taste) is normally more titillating than a dressed, but still people are attracted by different things. Someone will notice first in the streets women with great legs, someone else women with large breasts, a third one great faces, etc…
And I would point out once again that the face bear expressions, that give away a great deal of informations about the person and this plays an important part in attraction. An objectively beautiful face can become unatractive due to the expressions, while I’ve never seen an expressive pubic area.