(Sorry if these comments are a little haphazard; I wrote them as I was playing!)
I loved the introduction! It felt like an opening cutscene, or a film scene that plays before you see the movie title.
Your writing is clear and expressive, as is the conversations! Dorian’s personality comes through in both the dialogue choices and the exposition - a personality that seems to be short on patience, confident, and vain - though in some instances, some of the language used feels a little more modern than in others.
Some bits of exposition felt a little bit long, though I liked that they gave me the feeling that I was reading Dorian's thoughts. Maybe integrating those thoughts while talking about Dorian making a facial expression or moving about the room or something might help it to feel more unified.
I was a little confused at how Dorian was wondering about disappointing Basil, while the latter had smiled when he went to dance with Henry.
I knew something was going to happen with the painting, but I wasn’t expecting that ending! It felt powerful, though it did feel a little sudden. I'm not sure if I caught on earlier in the story about the painting being a literal reflection of Dorian - or vice versa? - but once I did, it made sense!
All in all, I really enjoyed this!