Wow. I wasn't expecting so many replies.
First of all, thanks to everyone. I'm trying to get accepted at iStock as an illustrator but it hasn't been easy. Once I do, I definitely intend on selling vector files there, so I think I'll have to learn a few extra things. I do know how to create shadows and all that on different colored surfaces link in this image (the tree shadow) -
(http://static-p4.fotolia.com/jpg/00/23/64/39/400_F_23643953_MoyD0HSPmeWLx6OONOK4KudtyBtcxALA.jpg)
Augusto, I always have a look at your portfolio and you sales on Shutterstock impresses me! That's one of the main reasons I'm attempting illustrations.
I'll now try to make some more challenging images! With me luck!
Ohh... can I use the Mesh Tool? Will it be AI8 ou AI10?
Thanks again!