A skep body appears to be human, and that appearence is as varied in size and colour as humans are. However, where Skeps differ is that a Skep is more than one body. Commonly, a Skep is 4 bodies, all of the same appearence and all sharing the same single mind, but able to operate independantly. Think “the borg”, but with more personality.
The number of bodies that a Skep has CAN differ. Some are born with only 2 bodies. There have been some with as many as 7, but they tend to go mad.
Skep have advantage on perception roles, but disadvantage on wisdom saving throws.
In battle Skeps can use 2 actions per turn, but action, movement and bonus is split across each body. So for example, body 1 might use the first action, body 2 the second action, body 3 the movement and body 4 the bonus action each turn). The bodies all have the same stats, initiative and HP (so damage to one body damages all four), although they may carry different weapons.