I thought most SC nominees originate from the Appellate Courts. If he can't appoint real conservatives to the AC then he won't get them on the SC either.
Not necessarily true. Thomas wasn't a judge. Neither was Blackmun or Marshall. Warren was a state justice, as were Sutor and O'Connor. In fact, I'm not sure if any of the justices currently on the Court came from the federal appellate system. Technically, you don't even have to be a lawyer in order to be on the Court.
Marshall was the general counsel for the AFL-CIO. Not exactly good training for the Supreme Court. Blackmun was a lawyer for a healthcare institution.