A physical description of Alec d'Uberville is in Chapter 5 of Tess of the d'Ubervilles:
He had an almost swarthy complexion, with full lips, badly moulded, though red and smooth, above which was a well-groomed black moustache with curled points, though his age could not be more than three-or four-and-twenty. Despite the touches of barbarism in his contours, there was a singular force in the gentleman's face, and in his bold rolling eye.
Here Alec is described as the stock villain of Victorian novels. His swarthy complexion reflects the English bias of those who are darker skinned as more capable of unethical behavior. While Alec is only twenty-three or twenty-four years old, this description of him with the handlebar moustache lends him more maturity of age along with the sinister appearance.
It would also seem appropriate to depict Alec d'Uberville with somewhat of a sneer on his face as he obviously has no human respect for the ingenuous Tess as he first terrorizes her by having the horses race along as they are in a carriage, and then later rapes the innocent girl while she sleeps in Chapter 11. Indeed, he is a predatory type, who selfishly indulges his own desires. Thus, a cyncial scowl upon his face may be befitting of his barbaric character. The use of dark colors in this visual representation also seems appropriate.
One real-life example of a Victorian villain is Jack the Ripper, so a little research done on him may afford more ideas on how to depict Alec d'Uberville. There are a number of websites that give access to Victorian villains, as well; see one link below.