I am very easy-

don't claim it as yours if I made the majority of it. Thats it. (Absolutely feel free to credit yourself before me if you gave me heavy directions. <3) 
if you change pattern/colours too much it isn't mine anymore - I don't want to be credited for heavily edited versions/versions where the vision is altered beyond recognition. 

Feel free to edit over my art! Specially when its trait updates etc, but ultimately I do not care. You paid me it is yours. Just put a edited by (whoever did it) in the credits. <3