Are you dealing with ProjeQtOr feature or Forum ?

ProjeQtOr of course B)

So this feature already exists in V5.0 : in user parameters

In normal user parameters, I can't upload a picture. There is not button to do it.

I can do it only when I'am connecting in admin mode.

This is an issue on V5.0 : if "access to data" is "read only" on user for profile, user cannot change Avatar.
This issue is fixed on V5.1.

Where is "access to data" option ?

In Parameters >> Acces Rights >> Access to Data (not project dependant)

Thanks it's ok now.

In 'Access to Data' all options was set to 'update' but I think it is not the real value in bdd.
I saved again and now it's ok.