I mean, if you do the typical setup with an elf, dwarf and halfling, it's too derivative. All the "standard" D&D races are yanked straight from Tolkien. Why not actually use D&D races in a D&D movie? Main guy is human, but, his buddy is a dragonborn. What's the problem?
I think you have a good point, there.
Hmmm...how about this for an adventuring party:
1) a young human warrior fresh off the farm- let's make her a woman, maybe even a Warlord type- who was magically whisked away from her homeland
2) an Awakened wolf who has been her companion her whole life
3) a Warforged ranger who is searching for his lost love
4) a Wemic barbarian who cannot find the ability to Rage
5) a Scarecrow bard whose mind has been clouded
And they're all off to go talk to a powerful arcanist for help in their respective quests...
But seriously, I DO think it would be cool to have something like a Lizardman or Dragonborn included in the party as a silent hulking, hooded figure...until his true nature is revealed. Or a Githzerai monk whooping asses with his quarterstaff.