The answer is No, at least if your definition of a "nice" distribution includes anything in the convex hull of distributions that arise from time averages.
Time averages from a steady rotational flow on the circle $S^1$ will produce Lebesgue measure $\mu$. Time averages from a flow toward an attracting fixed point at the north pole $P$ will produce a point mass $\delta_P$.
But there is no flow on $S^1$ whose time averages lead to $\frac{1}{2}(\mu + \delta_P)$. (Consider the orbit of $P$.)
You can generalize this to flows on $\mathbb{R}^n$ by embedding $S^1$ as a global attractor, and generalize to continuous maps by replacing the rotational flow with an irrational rotation.