Fall out boys music, image and persona has changed over the past 8 years, the typical emo convention has been fluent throughout.

For example in one of the bands first music videos 'a little less sixteen candles a little
more touch me' the band wear dark colored tight clothes,this is a typical convention
of emo bands and has almost became a calling card for the band.
The band also experiment with unique, individual hairstyles, i believe they do this to get a reaction out of people and to cause controversy, which after all is what emo is all about.