paintbrush used for piece:

http://www.youthedesigner.com/2010/07/08/31-sets-of-free-photoshop-paint-brushes/

 Shell Sketch:

Shell used to draw the shell

 http://www.publicdomainpictures.net/view-image.php?image=296&picture=sea-shell



Image used to draw sand

http://www.publicdomainpictures.net/view-image.php?image=11566&picture=boardwalk-on-sand