Yeah, take a troll for example. They vary as tiny pests, all the way to giants that wield a club.
Really, the only universal trait between them is that they are ugly. It all depends on what you imagine, or in this case, whoever made the djinn.
When I think of a djinn, I picture the genie from Aladdin, mainly because I grew up with magic the gathering, so I've been told that djinns are pretty much a genie without a lamp.