Unlimited Kayo-chin works.
Okay, so there's quite a bit of artists...
Top left corner: あるふぁ
Top left center: ノブレス
Top right center: たらちね
Top right corner: Pas
Middle left: 佐倉赤身
Middle (the large Hanayo): ふうあつけん
Middle (one to the right of it): 九千ビノレ
Middle (once more to the right): さまたもとき
Middle right: つるぺ太
Bottom left corner: おいつき
Bottom right corner: @kuen3
Phew! That took awhile, but it was great fun. Happy Birthday, Kayo-chin!~
Next birthday is Umi-chan's, on March 15th. See you then!