カタカナのユセージュコンディションズはおもしろいですね。
ヘアアレンジ :: "hair arrange," hairstyle :: loan phrase (Jelly Magazine)
カワイイ :: kawaii=cute :: emphasis (Jelly)
ヘアメイク :: hair & makeup :: loan compound (Zipper Magazine)
クリスマスシーサン :: Christmas Season :: loan phrase (Zipper)
マキアージ :: Maquillage :: French loan word, brand name (Zipper)
ブラックニーハイブーツ :: black knee-high boots :: loan phrase (Zipper)
トレンド :: trend :: loan word (Zipper)
カンタン :: kantan=easy :: emphasis/simplification (Zipper)
リアル :: real, realistic :: loan word (Zipper)
I think it is curious to see originally Japanese words written in Katakana, like "kawaii" and "kantan." The example of "kawaii" that I found appears on a cover of a fashion magazine so I think it is written this way to be more eye-catching; katakana is more angular and bold than hiragana. Also, in terms of emphasis, you can imagine someone exclaiming "Ahh, kawaii desu ne~" over something on the magazine, and this is probably the impression they want to give you -- there are lots of things inside that are super-kawaii (haha).
The usage of katakana for "kantan" is odd. It appears in Zipper, a magazine targeted to teen and tween girls. Nazikian-sensei suggested that the kanji for "kantan" (簡単)might be too difficult for kids of this age. But in that case, why use katakana instead of hiragana?
I think it's interesting how foreign words are given Japanese grammatical structures; for example, "real" becomes a "na"-adjective (like "handsome"). Also interesting is the presence of non-English loan words like "maquillage," we are so anglo-centric that we often forget Japanese borrows from other languages too.
"Black knee-high boots" is just really funny! It's so specific! And "Christmas season" is so cute.
The textbook descriptions of katakana focus mainly on its use to spell foreign words, but these examples show that it's quite often used for other purposes. And furthermore, some of the loan words are originally borrowed from English, but have evolved somehow in Japanese and make no sense in English anymore (like "hair-arrange" and "hair-make"). So even when katakana is used to spell loan words from one's own language, the interpretation might not be so obvious.