Formal:
* J'adore vos photos. (This is the most literal translation and is perfectly polite.)
* Vos photos sont magnifiques. (This means "Your photos are magnificent.")
Informal:
* J'aime beaucoup tes photos. (This is a more casual way to say "I really like your photos.")
* Tes photos sont géniales! (This means "Your photos are awesome!")
* Tes photos sont trop belles! (This means "Your photos are too beautiful!")
Adding a personal touch:
* J'aime beaucoup la manière dont tu captures la lumière dans tes photos. (This means "I really like the way you capture the light in your photos.")
* Tes photos me donnent envie de voyager. (This means "Your photos make me want to travel.")
Choose the phrase that best fits the situation and your relationship with the person.