Dwarf Neon (Praecox) rainbows are very attractive fish. Schoolers, a nice group would be 2-3 males and 4-6 females, depending on the size of your tank. Males have the red fins, females the yellow, so they are very easy to sex. Bodies are incredibly iridescent (that picture just barely does them justice), and the males will "flare" at each other as well as flare for the females to attract their attention--it is really beautiful.
The only warning I would give about them is that all rainbowfish tend to be susceptible to columnaris, especially the "mouth fungus" variety. So if you get them from a pet store, take a very, very, VERY careful look at the mouth area and make sure there is no signs of anything white & fluffy looking, no signs of any sort of lesions near the mouth, etc.
I made the mistake of not checking closely and ended up with a school of 5 of them, all of which had full-blown columnaris within a week of me getting them home. Despite my best efforts, none survived.
Another species of rainbowfish you might consider, either in addition to the praecox or instead of them (again, depending upon your tank size) is the Threadfin Rainbowfish (Iriatherina werneri). Like the dwarf neons, threadfins only get to about 2" (some sites say only 1.5") at full adult length. I have seen them in person--one lfs
near me sells them--and they are quite spectacular. Nice picture of one of them can be seen here