It is Japanese English that stands for ”イメージチェンジ”.
It is a noun that means “makeover”. It is used to describe a person/thing that gets a new look. ”イメチェンする” is the verb form.
Meg is thinking of what kind of hairstyle she should get for autumn.
- Meg: I'd like to change my look for autumn.
秋に向けて、イメチェンしたいな。 - Amy: Me too. I decided to dye my hair darker.
私も。髪を暗く染める事にした。 - Meg: I see. I wonder if I should get my hair cut to shoulder-length.
なるほど。肩まで、(髪を)切ろうかな。 - Amy: That's nice! I think it will look good on you.
いいね！似合うと思うよ。
Ken and Leo are talking about the construction around the station.
- Ken: There's construction going on right near the station. What are they building?
駅の近くが工事中だけど、何の建設だろう？ - Leo: I’m not sure, but the oldest buildings were totally outdated. It seems it needed a makeover.
よく分からないけど、建物が古臭くなったから、イメチェンするらしいよ。
Meg and Ken are talking about Sara.
- Ken: I didn’t realize that Sara was that pretty.
サラって、あんなに美人だったっけ？ - Meg: She was already pretty, and now she is looking better than ever! I feel like she got a makeover. Uh-huh, maybe she has found her new date.
元々美人だけど、最近さらに綺麗になった！イメチェンした気がする。あーなるほど、たぶん、彼氏ができたな。 - Ken: What? I wanted to ask her out so you mean it’s too late to do it...
えっ？デートに誘おうと思ったのに、遅かったか... - Meg: I’m afraid so.
そうだね。