Depends whether you want personality or colour. Cichlids have personality but the colourful ones are generally too difficult to keep alive in general communities (blue/gold rams and apistos), or too aggressive to be with small fish (jewels, convicts etc). In my experience, hardy and good with small fish are Bolivian Rams, they can be pretty if you can obtain good stock, but they aren't really 'stand out'. Keyholes are cool but not colourful and you would have to watch 'very' small fish.
Gouramis are colourful and normally good with fish quite a bit smaller than themselves. Not always very hardy though. The golden gourami is one of the hardiest and colourful, go with some 2" shoaling fish and that could be quite cool, although they can be quite nasty to each other if you get more than 2. They get to 6" so you would need a fair sized tank of at least 100 litres. There is also the blue version of this type. I hear pearl gouramis are also cool and work well with smaller fish, i'm thinking of getting one myself for my smaller tank (160 litre) with smaller fish.
Platy, mollies and swordtails are colourful but lack personality for me. So not an ideal 'stand out' fish either.
Dwarf plecos are awesome, pretty much ok with smaller fish but they are expensive and they hide a lot, so are more of an enthusiasts fish than a centrepiece. I have quite a few.
Smaller fish wise, cardinal tetras are easily the nicest as far as i'm concerned, although best in at least double figures. They are apparently hard to keep, but although i did put mine in a mature tank i've had virtually no problem keeping them alive and looking good. Harlequins school nicely, but look out for good stock as i see a lot of ropey mass produced ones. They are colourful as well. Best in 8's plus. And for your tank's upper region, a big school of hatchets are great, although you need a tight lid. I have 12 black winged in my 160l and they are the best type. I have 6 platinum in my 210l with bigger fish. They get to 3.5 inches. I also like emporers, nice colours and graceful, but they don't school. A school of glowlight danios look pretty good as well, although i prefer the similar coloured Harlequins personally.
And a school of cories always look good for the bottom, the jullies particularly.
Hopefully you'll get a few ideas there.
