I have started a binding to the GD graphics library here.
It currently supports only a tiny subset of the functions (mainly drawing primitives) included in this library
and will likely never be complete as it is purely a hobby project.
But as the GD library already exists for a long time, is easy to use and popular in
some fields), someone might still find it useful.
It is not the first Fortran language binding to the GD library, but the other approach I found
here seems to be nearly 19 years old and not using iso_c_binding for the language binding.