Scenes from say CALIGULA (the feasting scenes, not the sex stuff) or other said Roman movies (like maybe GLADIATOR?) could be inserted for the sake of showing Senators or rich people in general enjoying themselves (as well as come across as gluttoness and weak). Or, if it's possible, say during a scene when Sideous is walking down a corridor talking to Maul or someone else, you take said scene and put it in a room they pass or in a room/window in the background, with the implication that Palpatine/Sideous sees the avarice and gluttoness behavior of what the Senators do behind closed doors and it is what is propelling him to create the Empire to begin with (along with the threat of a neighboring Empire taking them over).

That might be very difficult to take footage from different films and get them to match. Than again, Trooperman did it somewhat with Dune and AOTC.