The [`/me/associated` route<sup>Doc</sup>][1] *is* the preferred way to turn an `access_token` into a list of users, it returns the collection of per-site user details that can be quickly fetched.  It's basically the user's [account tab][2].

If you need more details about a user on a give site, then turn around and hit `/me` (or `/users/{ids}`) on the sites you've discovered via `/me/associated`.

As for display names and profile images, you will have to make at least one call to a site specific method; I typically advise consumers to only query the user's top account (by rep) for that information, it's the same on all sites for > 90% of users with multiple accounts (and > 50% of users only have accounts on a single site).  However, if you intend to display all of a user's accounts you will have to make multiple requests.


  [1]: https://api.stackexchange.com/docs/me-associated-users
  [2]: http://stackexchange.com/users/27899/aldrin?tab=accounts