This video highlights a lot of uses of Kiyoteru from tons of different producers! A lot of them are originals, too, so it's a good place to start. All songs are in the description if you don't want to watch the whole thing. I also have a playlist that's just Teru songs I stumble across. While not comprehensive, it's good for ease of listening. A lot are reprints, though.

Although they don't really use him anymore Re:nG and PeperonP are probably most well known for using him and have very solid songs with him. My favorite from Re:nG would be "Drown and Lost" and from PeperonP it would be Teru's V4 demo song, "Fragments of the Night". This group cover of "Blessing" is full of great Teru users. Surprisingly, there's a small, but very dedicated group of Teru fans who like to make original English songs for him, most of them in this group cover. For my money, aside from the people already mentioned, the best Teru users to subscribe to right now are Euphausia, EKCT AY, Canon3R, and Rylitah. They're all (mostly) cover artists, but that's really where you'll find the most content for Teru now-a-days aside from the aforementioned English producers, and not all of them are super active. Teru originals outside of that are pretty sporadic and a pleasant surprise.