optimizing my images!

[kelly]

my thumbnail quality drastically distorts my art which is clear and precise. what do i need to do to format my art so that it looks as good as the examples featured? does it have to do with image size or extension? even when i resized my jpg image and uploaded it, the image wound up blurry and distorted. please help. thank you.

kelly

[xyzbarna]

see the original image and the thumbnail would help