I'm going to guesstimate it's maybe 50cm x 30 x 30 ish then? Where 50cm is the length of it from left to right?
If so there are lots of options, but like I said it depends what you can get hold of in your area. If you're feeling brave you could maybe look into ordering some killifish eggs online to hatch out and grow on. Lots of the annual varieties are very colourful and easily got hold of. They also (generally) will mix well with peacful tank mates which is a plus. Although you'd obviously want to check before ordering.
An alternative might be something like freshwater gobies, there are some really pretty peacful gobies around.
Or some of the smaller ornamental plecos.
There's also the 'bog standard' community fish, but you could set the tank up in such a way that would allow them to breed. For example a m/f pair of honey gouramis (these come in red, yellow and wild type) with a shoal of corydoras for the bottom, you're a bit limited cory wise though (due to tank size) so you'd have to stick to some of the smaller species such as panda or pygmy.
There are some apistos suitable for 10gal tanks as gville mentioned.
You also might consider a male paradise fish with a shoal of dithers such as ember tetras, galaxy rasboras etc.
And I know you said you want big fish, but don't rule out a species only tank of shoalers. Literally just 1 species, but a large group of them. For example in a 10gal tank I reckon I'd happily put a group of 15 ember tetras in without a second thought. Black background, lots of green plants (can be fake) and any red fish will really look stunning.
