I sell cels on ebay quite often.  The best thing 
you can do is get a really GOOD scan of the cel.  
The better the scan the better it will sell.  
Having a link to the pencil sketch is great too 
if it includes the pencil.

Always include as much info about the cel as you 
possibly can.  Let people know what forms of 
payment you will take (ie: paypal, money orders 
etc)

AND the most important thing ... well to me lol 
if you don't want to ship out of the states, you 
can choose this option in the listing.  I only 
sell to Canada and the US only cause shipping out 
of the country is sooooooo expensive *_*

I hope this helps ^_^