I have pale skin so my body is always like a road map! haha just because the skin is translucent enough to see many of the veins since they are darker than skin. If I gain a little weight they are less visible, if I lose a little weight they become more visible, because the fat, as it insulates, also conceals to an extent. The insides of my elbows have always been particularly noticeable, that is partly because they are closer to the surface there, thus the reason why they like to take blood from that location.
But that would be an overall thing, not really in particular spots.