What other songs should I put on my ipod?

I have a lot of fast-paced songs for work outs from artists like Katy Perry, Stereo Skyline, and All Time Low, but now I want some calm, relaxing songs. I really like Taylor Swift and a few songs by Green Day, like "Wake Me Up When September Ends" and "Good Riddance/Time of Your Life." What are some other relaxing songs I might like? By the way, I'm a 16 year old girl. Thanks in advance!