... but what about those cases where you don't know that person was an infant or not? And when do they change from being an infant to a child, or from a child to a youth (one which is likely still to young to be a parent)?
... and what if you don't know the gender? (there are plenty of those)
In many cases, some variation of "died young" is used to indicate "this person died before they were likely to be married, so don't join them with a spouse".
Many prefer the simple "Died Young" to the "Died without Issue" that is often found ... that latter says nothing about whether that person was ever married or not, but the former implies they did not (likely) have a partner.
Another way to look at it might be "<this profile name> Died Young" as the grammatically correct way of 'reading' the profile.
Other variations of "Died Young" are feasible, and having examples in the media library of this project would give people choices to select from. In general, few would object to a more specific 'placard'.
I would simply encourage consistency in a particular area of the Tree for how any of these 'placards' are used -- and that convention can be decided by the active managers of profiles in that area.