Well, if you really want to start steaming, there is no artist acknowledge on the White House web site for the presidential and first lady portraits:
http://www.whitehouse.gov/history/presidents/
http://www.whitehouse.gov/history/firstladies/
I emailed them quite some time ago to bring this to their attention, but I see it has not changed. Perhaps if everyone writes to them this might help.
As far as I know, there are no good images of the portraits yet available on the web. I've emailed Simmie to see if he already has a scan he can email to me or if he will send material for me to scan.