jsf:graphicImage takes a url to the image,
to render image object you should:
1) make sure the image object (your entity or at least its image field) is available after request,
for example if your managed bean scope is request the object will be wiped out
2) create a mechanism to convert object refrence to a url and back
3) give the image refrence as url to jsf:graphicImage
if you want a simpler approach use seam image tag!
this way you will just give the image field name to the seam jsf image tag, and it works!