Well what would you like your sump to do. By definition a sump is simply another tank/water container plumbed into the display tank that is normally invisible.
Mine has a first compartment where a skimmer sits, then an algae filter, then a 3 compartment where the return pump sits. I also keep my heater in the third compartment. So mine is a filter, a place to stick ugly stuff (skimmer, heater, autotopup) and some extra water volume