Okay, before I get this started I need to preface the concept with opinion: I personally don't need to see any more classic characters in EpIII - I didn't even need Boba in EpII, but I do see how that could be interesting for his biggest fans.
IF you found out your job was going to be placing cameos of OT Classic characters - who would you place and how would you do it? I'll start with just one.
Han Solo - show him as a kid approx 10 years of age getting in trouble for something. Has nothing to do with the main story, just a cameo for fans of the OT (I must admit I've stolen this idea from someone else here who posted it long ago - sorry, but I don't know who).
Who else? Lando? Tarkin? Luke and Leia? Vader????