This will depend on your decorations. If you have a lot of caves or territories, you can add other non aggressive cichlids such as Severums, Firemouths, Geophagus or parrots. You can also keep Metynnis species such as Red Hooks, Silver dollars, etc. You can also keep fish like Arrowana as long as the tank is well covered and you get the smaller specie (Scleropages jardinii). ( You may need to rehome the arrowana when it gets large
) Then there are the bottom fish like catfish varieties.
So you have a few choices but keep in mind that a nice tank of just Oscars is also an option.