Not so recently, I had made a wallpaper about a serie named K-On!, and it got deleted. I received a message about low effort and then I started a new tread in Sandbox forum. If you want to look at it, it's here.
After many changes I submitted my last version of my wallpaper and it got deleted too. I received the same message but at the end there was a note from admin: "Background is too overfiltered."
My wallpaper's last version is here (Please look at the widescreen one.)
I didn't understand what to do. If you answer, I'd be glad.