I tend to make my characters look like myself, but with exaggerated features. Not overdone to the point where it's unrealistic looking, like most people make, but just enough to make the character look starved, fat, etc. Depending on the mod however, like Vikingr, I try to stick with a realistic looking character from the time period. So, maybe a very gaunt face, with a heavy set jaw, large beard, period-correct features and hair, etc.