Ooooh I love questions like this!
My tastes in fish have changed significantly, now that I have had pretty much everything I dreamed of having (well that can fit in a 55 gallon, I still dream of silver black tipped shark catfish) I personally think I tank that has a few, largish, center piece fish complete with some catfish (or loaches) best. Or "monster" fish.
Here's my three "dream" tanks
1) Coldwater- fancy goldfish (I only like fantail/veil tail) with gold dojo loaches (a nice school of 4-6) since they like to play in be with friends
Maybe 4-6 goldies and 4-6 dojos? (A tank like this will always be active and colorful, and I personally think fish that are like snakes are pretty awesome to watch)
2) Big fish little fish- A pair of moonlight gouramis (they are so pretty and gorgeous fish in my opinion), a large school of these "spotted" cories (maybe melanstus(?)
http://op5.triadinet.com/elmers/nlcatalog.asp?loc=nlitem.asp&args=sku|210 a pair of angelfish, and a large school of cardinal or larger tetras (OR take out the tetras and cories and do a large school or spotted pictus?) (moonlight gouramis and angels can be breath taking as they get older, and pictus are extremely active in schools and very pretty silver fish)
3) Monster fish- A birchir (I love these guys!)
http://www.aquamojo.com/bichir/Bichir 5b.jpg (he looks so cute!) with a few (2-3) large cichlids (These guys always will catch someones attention, because they have a bad donkey quality too them)
Good luck on whatever you decide and definitely post pictures!