If you just want the complete skin list so far, here it is!
Feel free to edit when you found a new skin and wanted to share it to the others or when there is an error.
A[]
Android 4 Kitkat by -makoto yuki
B[]
Basic skin, the second innovation by vahn10
Blackout 2 by Lolzep
C[]
D[]
DJMax Osuka by Xiao
DJMax Trilogy by TouchFluffyTail
E[]
F[]
Flat Surroundings by Haskorion
Formal & Simple by Martinawa Hatsuhi
G[]
H[]
Hatsune Miku Test by elzapatoverde
I[]
IA - Aria on the Planetes by Elzapatoverde
K[]
Kagerou Project/Mekaku City Actors by elzapatoverde
L[]
Luminance - The Science of Color by Uruoki
M[]
Mahou Shoujo Lyrical Nanoha by MLGnom
Minimalist by Inori
N[]
NeOsu 5 (NeOsu Surge) by OsuMe65
Neon Flower Style by Haskorion
NeonFX by O2MasterFX
Northen Ocean Hime by -[Jess-]
O[]
Orange skin by Inori
P[]
Puella Magi Madoka Magica by nomen
R[]
Rainbow Dash by ztrot and Quaraezha
Reisen Udongein Inaba by MLGnom
S[]
Senki Zesshou Symphogear by Kurokami
Shingeki no Kyojin/ Attack on Titan by RA272Nirvash
T[]
東方Project - Hata no Kokoro by Elzapatoverde
東方Project - Hinanawi Tenshi by Elzapatoverde
taikomania IIDX 13 DonderfuL by crystalsuicune
TECHNOCANDY by Garin
The Furry Skin! by TaitoTheHusky
Twilight Sparkle by ztrot and Quaraezha
U[]
Unbreakable Machine-Doll by Kurokami
V[]
Vocaloid Project Skin by NoClue
Verin by Beatstatic
W[]
X[]
Xenon by Chikilin00
Xi-Style G2 by Xiao