Easy Pictures To Paint

I sketch down. Now I would like to add a picture I just like to serve as a backdrop. So ... How do I do?

This question would have been more responsive to the software section, not art.

However, perhaps this link can help you.

http://paint-tool-sai.deviantart.com/

I add sand to my painting to give it more texture. Sawdust absorbs too much moisture in the acrylic paint for most of my needs.