Properly sizing and aligning the flex item(s) on the last row
Using flexbox, create 3 or 4 "phantom" items that always occupy the last slots.
So, for instance, user #82 is currently your last entry.
Make fake users 83, 84, 85 with visibility: hidden.
Alternatively, try just one phantom item at the end with visibility: hidden and flex-grow: 10. Target it with :last-child or :last-of-type pseudo-class.