I've know a lot of women women with Size 10 feet. The only time I really would have realized they have big feet is when I've seen their shoes left somewhere in the house. Yes, the shoes do kind of look surprisingly big when they're by themselves; but of the women I've known who have feet that big, some have just been very tall women (smaller feet would look wrong on them), and some have just apparently had a good-sized skeleton.
One very attractive young women I'm thinking of (not awfully tall, probably average height) has always had a super-slender, somewhat muscular, ballet-dancer, type build. Nobody would even notice that she has Size 10 feet. She has a perfectly slender, fit, physique. The size of her feet isn't anything anyone would even notice. (I suppose, in her case, if she were to gain weight her shoulders would fill out, and her good-sized frame would make her look like an "overall big" woman. She's so slender and fit, though, it isn't even obvious that her frame is, I guess, a little bigger than a lot of other women of her height have.
One of my girlfriends was 5 ft 1, but she had either a medium or large frame. She was slender and had a nice build, but she was self-conscious about her Size 8 feet. Again, they weren't anything anyone would notice (although I do have to say that were very weirdly shaped and maybe it was best that watched out when it came to what kind sandal she'd wear LOL ).
If someone like this were to gain weight, then she'd just be that "overall bigger" woman, and her feet would match.
As far as men go, I think it's a pretty similar thing. To me, all but the smallest of men's feet are big feet. I don't think big feet are noticeable on slender people, and on those larger-framed, heavier, people the feet match the rest of the build.
In general, a person's foot size is tied to his skeleton size. The only thing people with big feet need to think about is that if they're ever looking at one of those weight charts that tells people what their weight should be, there's a good chance they shouldn't be looking in the "small-frame" column. :)