Sorry, they're releasing images in two days. Seriously, though! Not everything has to be instant. They're putting themselves out to gauge interest and probably lure OEM vendors to their booth at MWC.
"and probably lure OEM vendors to their booth at MWC"
This is the whole problem, isn't it? When Google wants to make a device, they call up Asus or whomever and have it made. When Apple wants to make a device, they hire folks to do it, and those folks call the manufacturers for the parts. Why does Canonical expect the OEM to call them first on the basis of pretty mockups?