Could look at the bleeding Heart Tetra, i have 5 in my tank, i quite like them, would get another 5 if i could ever find any similar size.
Black window Tetras are quite nice, Red Eye Tetras are a little agressive, deffiantely get 5 or more of any.
If you dont like the Rams, you could look at Kribensis, very rewarding fish when breeding, moving and caring for their own fry. I love mine, only had them a few weeks but they are ace. You cuold also look at Pelvicachromis taeniatus, Striped Kribs which are great if you can find them.
How about some corydoras? I've got about 24 in my tank, great little fish, very fun to watch but also quite shy. 6 or more Sterbai's would be good, 10 would look very nice. Trouble is they are an addictive little fish.
Could revisit the Tiger barb idea, still ok with he Harlequins.
I have 12 in my 90 Litre, once its fully cycled i'll probably bump it up to 20 and chuck my Kribs in there too, should look nicely stocked with a few pots and plants:
over to you really, have a mooch around your local fish shops, see what you fancy.
You got options of small plecs too, or bigger if you dont mind the mess they make.
One thing i can say about the Tiger Barbs is that they are extremely bold and curious, they certainly dont shy away from any activity outside the tank. Which is nice, because everything in my big tank buggers off and hides when i walk past or get close.
