Depends on the gouramies... I'm always saying this, 'gourami' is a very general term - it includes the familiar
trichogaster and
colisa species, the giant
osphronemus species that get to 30", the tiny
trichopsis sparkling gouramies, tiny licorice gouramies,
betta species of all shapes and sizes, fragile chocolate gouramies and aggressive paradisefish and many, many more. Which ones were you considering?
240 litres is it? That's about 60 gallons and could make a
very nice gourami set-up. Putting all modesty aside, how confident do you feel about keeping gouramies and how much effort are you prepaired to put into this? Are there any other species you know you'll be getting (besides gouramies)?
Basicaly, there are various beautiful but extremely fragile species that would make wonderful additions - things like
sphaerichthys vaillanti for example.
http/www.practicalfishkeeping.co.uk/pfk/...?article_id=322 (a small, but pretty, picture).
If you feel you'd rather stick to hardier species, there are still plenty of stunning choices and, as they are more forgiving and more adaptable, are the way to go if you have other fish species planned that won't quite work in a specalised tank. Things like the stunning pearl gourami, croaking gouramies, sparkling gouramies, honey, thick-lipped and banded gouramies - and several other more common, relatively peaceful species - would fit into this category.
If you are interested in wild-type bettas (or, indeed,
betta splendens), they are an option also.
One thing I can tell you is that it' best to go for a maximum of around 6 top-dwelling medium-sized gouramies or around 7-9 of a smaller top-dwelling species plus some mid-dwelling species for the middle layers. Unfortunately, there's not much you can get as far as bottom-dwelling gouramies go (ctenopomas/microctenopomas would fit the bill but are african) so a few non-gourami bottom-dwellers plus a mid-schooling species would make nice additions to balance out the tank. Perhaps a pair of some kind of dwarf cichlid or a similar bottom-dwelling, center-piece type fish could also be included.
Like I said though, you need to provide a little more info. What exactly did you imagine yu'd be doing with this tank and what sort of prefference do you have as far as the gouramies go and, of course, any non-gourami tankmates?
edit: A while ago, I could have sworn I'd replied to someone with a long list of all sorts of gouramies. I can't find the thread now so I'll give you this one instead:
http/www.fishforums.net/index.php?showtopic=119635 I only wrote about top-dwelling species and was taking into acount this person's other fish so it won't all apply to you but, at least, it can give you some idea of a few of the possibilities. if you want to see what all those fish look like, check teh pinned topics, the fish index and, of course, www.google.com !