I ran an all-Gnome campaign in second edition.
The characters were pregenerated by me, and all the information the players had to go on when chosing the characters was a set of 5 symbols I had inexpertly drawn. I had to tell them what they were - I can't even manage to draw a convincing tree, feather, rainbow, helmet and shield!
I then successfully manipulated the players into "choosing" the characters I thought they'd be best suited for role-playing.
Sounds like a recipe for disaster, and I'd never dare attempt it in these days of player power, but once they got over the initial unease of learning they were all playing gnomes everybody had a lot of fun.
Among other things, it led to a lot of party cohesion. Gnomes were rare in that part of the world, so they attracted attention wherever they went, and they quickly became a tight-knit team.
And they were, of course, different classes. Might prove too limiting to have same race and class.
(Speciality priest of nature, fighter-swashbuckler, illusionist, thief-troubleshooter and fighter/thief, for the record.)