Squished Illustration

[Mickeylayne]

I just submitted a piece of art (illustration), it was reviewed, and it's up for sale. However, I viewed the piece and the entire image appears "squished." The design is actually round. Could someone tell me if there's a way I could re-scan the art and submit it in a different format so that what the customer sees isn't skewed? It's a JPEG, BTW. I'm not very computer savvy, so please "dumb it down" if you reply. Thanks for any help you can give me, as I will be submitting more art in the future and I want to do it right!