You can use any of the artwork listed in this old thread: The Inking and Coloring Book Thread
Im not really great with drawing. Understatement But I enjoy using programs to colour art, so I was hoping someone could send me some/one manga picture to colour.
Oh yeah, and I would give you credit for the line work of course.
NP! Have fun coloring. There's a lot listed there... especially from me. xD