Paler flesh, maybe with a slight yellow tint. Thinner flesh drained of blood looks yellow and waxy. Matted fur. Maybe patches of exposed, blackened skin. Perhaps his posture should be stiff and unnatural, always looking a bit uncomfortable. Jaws tend to hang open. Eyes glassy and sunken in. All of those things might spell, "walking corpse" more clearly.

Hrm, most of these things seem more like zombie things than vampire things, and I can't make his skin yellow without it blending into his fur.

Old World vampires were indistinguishable from walking corpses. They were one and the same. "Zombies" only became a pop cultural thing because of those George Romero movies. You could break old ground!

replace his head with a bunch of tentacles, make his fingers worms, fill his torso with a bunch of tiny holes with parasites crawling in them, and give him clown pants.

...I don't think any of these things would work for what I'm going for. XD;

but it WOULD be creepy

You could make it part of his aestethic that he hides what would be obvious. His collar already covers his bite marks on his neck, his vibrant and flashy outfits distract from his gaunt frame, his eyeshadow covers up the sullen eyes.

Personally, I’m a fan of the design as is, and wouldn’t recommend much need for a change.

Yellowing sclera of a corpse. Darkening streaks around the eyes, mouth and nose.

I think his design is really rad as is 👉👈
but as a vampire, what if he had a more monsterous, manic, hybrid form 👀
could keep his current charm, while still giving him a lot of room for taking liberties with all sorts of creepy options.
gnarly vestigial wings, elongated fingers, half-bat ears, maybe a mouth that widens a bit too far, any number of things x3

Make him a lawyer, he will suck out your blood and your money

Maybe some red hue around the eyes, broken blood vessels like. Could add to it.