Absolutely. Well keep in mind that a fish like an oscar would definatly fit by the 1'' per gallon rule, its not a good idea in your case lol. I would recommend smaller aggressive fish like 4'' max and some smaller fish around 1 or 2''
maybe 3'' tops on those. But i would suggest ONE aggressive fish with some community fish.
You could get a dwarf gourami and some danios, I prefer long finned danios to regular zebra danios because i like the look. Or some tetras (glolights or others, not neon tetras to start with, your just asking to feed them to an aggressive fish, besides that they die really easy). You could get some mollies to go with the gourami, or some platies, they all stay pretty small and are interesting to watch. If you like top water fish you could get some hatchet fish, i'm pretty sure they stay small, like 1-2 inches. Maybe some some corys for the bottom. Or guppies
Do you like german blue rams?
To me a setup with a dwarf gourami, (4 inches), some guppies or platies (or a mix of the two) say two guppies and two platies. that would be about 8 inches, so 12 inches right there to the rule. And some tetras with that.
Or instead of the gourami you could have a pair of gbr's with the same set up with the rest of the fish. Just remember, ONE aggressive fish with some smaller fish, if there is to much aggression and not enough fish to spread it around the stress can kill them over time. It also lowers their immune system to be so constantly threatened.
So i would go with one of those two set ups bud.