Have you looked on Pinterest? Of the Sweet 16's I've attended the most popular things for the teens were karaoke, photo booths, and sweets tables /bars.
My oldest turned 16 last year. At first she didn't want a party. She had no desire to be the center of attention. My nephew is 8 days older and felt the same way. They decided on a joint party. His mom and I rented out a room at a restaurant. We hired a DJ who also had a karaoke machine. We had a sweets table and a appetizers table set up. Decorations were black, white, and purple. Purple happens to be their favorite color, so that worked out. I made a Sweet 16 banner using those colors. I also bought purple Masons jars to use on the tables. The candy was also purple, black, and white. It wasn't a large party, but it was what they both wanted.