Wrack is a dragon. No, the picture isn't wrong. Wrack can transform into a human shape – it is by no means clear whether the dragons are humans who can take draconic form or vice versa. Wrack's response is to say that he is a dragon, which means he can be either form.
Wrack is one of the dragonlords who rule Sendaal. There are very few dragons in the land – they breed rarely, despite their efforts – but each one is a powerful figure. Wrack is one of the most significant of their number.
Wrack oversaw Sorrel when she was training to be a sorceress. There is no doubt that he found the young woman very attractive. Her views of the dragonlord were a different matter. When the humans rebelled against draconic rule, Sorrel was a major figure in the human air force, and she blew one dragonlord, Kabal, out of the sky. She had a number of aerial duels with Wrack, and he eventually brought her plane down. He snatched her from the wreckage and enslaved her. Despite eventually escaping his clutches, Sorrel never forgave Wrack for his treatment of her. Which is why, at the beginning of Sorrel in Scarlet, it was Wrack's mansion that Sorrel had raided.
Wrack is a laconic, sometimes grim figure, typically never speaking a full sentence. He is a strong and vigorous figure, and even Sorrel would have to admit that he is attractive in a dark, saturnine way. He also has a dangerously short temper and, like Sorrel, has a tendency to resort to physical action when he grows angry.
He is probably the most important person in the books aside from Sorrel herself – and Sorrel will tell you regularly and frequently how much she hates him.