LPT: If you want compliment someone’s looks but are scared of sounding creeping, compliment a choice they have made, not something they had no control over.

Complementing someone’s looks isn’t always a bad thing depending on circumstance, but if you are worried about how it comes off then try this:

“I love your dress” can sound less creepy than “you have great legs.”

“I love your hair style” can sound less creepy than “I love your hair.”

“I love your nails.” “I love your shoes.” “Your make-up looks great.”

Pick something they have made an active choice to spend effort on and show that you respect that effort.

Edit: As a caveat I’d like to add that, one, you have to actually mean what you say, and two, you have to have zero expectations. A compliment is a gift, not an exchange.