&#62; Tricks like appending ".jpg" to the url seem a little hack-ish to me. That feels like a parameter.<p>that feels like a file type. If there is more than one representation available then it's a parameter, indeed, but the standard place to put that is on the end of the filename.<p>Surely it's clear that:
employees is the collection;
employees/110 is a specific employee;
employees/110.jpg is the jpeg representation of said employee.