Gst on royality

Your qestion is not clear to me but as far i understood from above that u r paying some service to that company from where your remuneration will come then i will tell you that the gst is a destination based taxation if your place of supply of services is outside of india then it will be treated as export of services. then no gst attracts on it.

It is a print on demand US based e-commerce platform where I am the artist / designer , where I upload my designs and create virtual listing of various clothings,  home accessories etc and  e-commerce platform receives order from customers and that platform handles everything including printing and delivering the material to customers . The designer/ artist will get paid depending upon sales of his/her designs/ art work. My questions are 

Will this payment be considered  as export of services or royalty ? (Because I am not issuing any invoice to them as I'm getting paid at later date  for my art work / design depending on sales of products containing my design.)

If it is a royalty, then is GST applicable and who will pay it?

In case of royalty, under which head of income tax, royalty will fall and how much tax rate royalty attracts and which ITR to be filled if one of your source of income is Royalty ?