If the angelfish are small to start with, and the shoaling tetras are in with them from the start, I would consider disk-shaped tetras to be reasonably safe, but not linear species.
Flame Tetra I view as relatively disk-shaped, but they are small and would not be my choice. I would consider the Rosy Tetra, Bentosi Tetra, Ornate Tetra, maybe Bleeding Heart Tetra...these species are very much alike in their purplish/red colour, disk-shape, they are peaceful (the BH the one caution).
The other thing is the tank size...a decent group of angelfish means five or six, preferably more, and if the tank is only a 55g to 90g the angelfish will grow to fill the tank. Substrate fish like cories would be the best addition. A large shoal of one of the foregoing "Rosy" species. None of this is guaranteed, when dealing with angelfish. I have never seen angelfish at their best except in very large tanks by themselves (with cories, OK).
The thing we must keep reminding ourselves of, is that any fish in an aquarium is an artificial setting. In the habitat fish are able to keep away from other fish due to the vast expanse of the habitat.