As a user, I would find Mark's suggestion very confusing, accepting non-integral floats but not non-integral Decimals and Fractions.

I agree that ideally it should accept only integral inputs, including floats, but deprecating the behavior for non-integral floats has been deemed out of scope for this issue.  Therefore I suggest doing the same for Decimal and Fraction: accept them but raise a ValueError if their values aren't non-negative integers.

At a later point we could deprecate this behavior for all non-integer types of numbers.

Another alternative, which is also more acceptable IMO, is to raise TypeError if given anything other than an int or a float, while deprecating floats altogether.