Wear nice ("Sunday") clothes. Gentlemen should wear a coat and tie. Ladies should wear a dress/skirt & blouse/suit; or nice slacks and a matching top. No jeans (even new ones) unless it's a hoedown recital!
Try out your clothes ahead of time by playing your pieces in them. Your clothing should allow sufficient movement for arms and shoulders. If you are considering more than one outfit, play all your pieces in each one.
Steer clear of sleeves without cuffs. The sleeve may slip down your arm and cover your wrist and heel of your palm, thus making playing more difficult.
Leave the outrageous stuff to Liberace-impersonators. No capes, feather boas, and so on. Perhaps this is a Halloween recital in costume?
Ladies, avoid flowing "batwing" sleeves. They'll get in your way. They also will be a distraction for the audience. You want them to focus on your music.
Other ideas for ladies: Sequins and other "catchy" stuff is dangerous. You don't want your upper arm to get "hung up" on the sequins of your bodice when you are doing cross-hand playing!
Don't wear something that is form-fitting in the hips and abdomen so that you're fretting about whether you're "sticking out" when you're in a seated position. This is a terrible distraction for you, even though no one in the audience will be thinking about this!
Dangling bracelets are an invitation to disaster. Watch those shoulder-touching earrings, too. You don't need any "tickles" to break your attention. Or, to have them get "caught" in the shoulder area of your dress.
Young ladies, please, no exposed midriffs, ultra-short skirts (that ride up high on the leg when you are sitting in it or expose somewhat more of your backside than you expected when you bow), and other inappropriate clothing. See following discussion of shoes. Young gentlemen, please wear belts with nice slacks; tuck in your shirt. A tie is a nice touch. No shorts, jeans, or sweatshirts from either gender.
Give attention to your shoes! Make sure they don't squeak when you pedal. Make sure they don't slip off the pedal. Can you walk on and off stage without falling? High heels are usually not a good choice, if for no other reason than you might trip and fall. (Great beginning to a performance, huh?) Don't wear a pair of new shoes.
You probably already know whether you can play in your rings. If not, play it safe and leave them at home. Don't plan to drop them into a pocket. You might end up dropping them somewhere else by mistake.