In the NCT 127 special website (http://nct127.com/) there were uploaded some special photos as a reward, after the song Boom meeted the reward requirements.
You can see them below.
Also see the other uploaded concept/teaser photos:
NCT 127 Neo Zone ‘NEOZONE Discovery’ Concept Photos (HD/HR)
NCT 127 Neo Zone ‘NEOZONE Discovery 2’ Concept Photos (HD/HR)
nct 127 Doyoung NEOZONE Boom Special Concept
nct 127 Haechan NEOZONE Boom Special Concept
nct 127 Jaehyun NEOZONE Boom Special Concept
nct 127 Johnny NEOZONE Boom Special Concept
nct 127 Jungwoo NEOZONE Boom Special Concept
nct 127 Mark NEOZONE Boom Special Concept
nct 127 Taeil NEOZONE Boom Special Concept
nct 127 Taeyong NEOZONE Boom Special Concept
nct 127 Yuta NEOZONE Boom Special Concept