If I have a retail business and Global Sugar Art is one of my suppliers,...could I "copy" a picture off of global sugar art's website to paste to my website for my customers to view when they order from me off the internet? I hope that makes sense. Please let me know if my question is not clear and I will be more than happy to call you direct.

Any time you take anything....be it words or pix from someone else you MUST give credit to the creator. It's only common sense.
Put it this way: if you posted a cake pic and found it on the net being posted by someone else w/no credit given how would you feel?
Probably the best way to handle it is to put a link for people to goto their site.