This question is the easiest or the hardest, depending on the temperament of your loved one.
Some things you can do without being asked, like manicuring mom's nails and finding dad a robe that doesn't make him feel old. Locate their favorite movies, frame old photos and decorate their room to look lived-in. Candles may not be allowed, but few people will argue against mom's favorite scented soap in the shape of a seashell.
It might be enough just for you to be there, talking to the staff, checking up on things and making conversation.
Those are the easy things. Harder are wishes for more frequent visits, or simply to go home. You may not be able to say yes. But you did what you could -- you asked.