It might just be that people don't want to suggest much because we dont know what you like. You say you are getting rid of Oscars...why is this? Is it the care? The size? Just don't want them anymore? You want to branch out into other things?
As for branching out.... preferred substrate type? Live plants? Fake plants? Type of filter and flow in tank? Big fish or small fish? Really...it would be more helpful if YOU researched some fish that you might like to do and then post that list with your water parameters again and people can tell you what works and what doesn't.
If it was me I would do a humongous planted community...i love small fish though. You may not. It seems like you could have a ton of options with that size of a tank. You can get very creative if you wanted to!