A renderer ain't nothing but a class :)

GtkCellRenderer — An object for rendering a single cell 
GtkCellEditable — Interface for widgets that can be used for editing c
+ells
GtkCellRendererAccel — Renders a keyboard accelerator in a cell
GtkCellRendererCombo — Renders a combobox in a cell
GtkCellRendererPixbuf — Renders a pixbuf in a cell
GtkCellRendererProgress — Renders numbers as progress bars
GtkCellRendererSpin — Renders a spin button in a cell
GtkCellRendererText — Renders text in a cell
GtkCellRendererToggle — Renders a toggle button in a cell
GtkCellRendererSpinner — Renders a spinning animation in a cell
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https://developer.gnome.org/gtk3/stable/GtkCellRenderer.html

https://github.com/GNOME/gtk/blob/mainline/gtk/gtkcellrendererpixbuf.c

https://github.com/GNOME/gtk/blob/mainline/gtk/gtkcellrenderertext.c

this suggests the approach could work even though its not common custom gtk3 cellrenderer

https://stackoverflow.com/questions/14998298/how-to-write-custom-gtk-cellrenderer-in-python-and-gtk-3

Thanks for the information, I documented the solution as a new comment on the original question.

Gtk3::SimpleList->add_column_type('image_text',
        type => 'Glib::Scalar',
        renderer => 'Gtk3::CellRendererText',
        attr => sub {
            my ($treecol, $cell, $model, $iter, $col_num) = @_;
            my $pixrd = Gtk3::CellRendererPixbuf->new();
            my $txtrd = Gtk3::CellRendererText->new();
            $treecol->clear();
            $treecol->pack_start($pixrd,0);
            $treecol->pack_start($txtrd,1);
            $treecol->add_attribute($pixrd,'pixbuf',1);
            $treecol->add_attribute($txtrd,'markup',2);
        }
);

# Create your model

my $slist = Gtk3::SimpleList->new (
   'Text Field'    => 'text_icon',
   'text'  => 'markup',
   'icon'  => 'pixbuf',
);

# Hide text and icon
my @col = $slist->get_columns; 
$col[1]->set_visible(0);
$col[2]->set_visible(0);
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    # Defines a special column type that does not use a standard rende
+rer
    # The renderer is built by function 'column_builder'
    # The renderer will assume the first attribute of the model is def
+ining the icon to show
    # and the second attribute contains the markup text to display
    $class->add_column_type('image_text',
        type => 'Glib::Scalar',
        renderer => undef,
        column_builder => sub {
            my $pixrd = Gtk3::CellRendererPixbuf->new();
            my $txtrd = Gtk3::CellRendererText->new();
            my $column = Gtk3::TreeViewColumn->new();
            $column->pack_start($pixrd, 0);
            $column->pack_start($txtrd, 1);
            $column->add_attribute($pixrd, 'pixbuf', 0);
            $column->add_attribute($txtrd, 'markup', 1);
            return $column;
        }
    );

    # Build the columns list for this new tree
    # according to the definition of column types
    my @column_info = ();
    for (my $i = 0; $i < @_ ; $i+=2) {
        my $typekey = $_[$i+1];
        croak "expecting pairs of title=>type"
            unless $typekey;
        croak "unknown column type $typekey, use one of "
            . join(", ", keys %column_types)
            unless exists $column_types{$typekey};
        my $type = $column_types{$typekey}{type};
        if (not defined $type) {
            $type = 'Glib::String';
            carp "column type $typekey has no type field; did you"
               . " create a custom column type incorrectly?\n"
               . "limping along with $type";
        }
        push @column_info, {
            title => $_[$i],
            type => $type,
            rtype => $column_types{$_[$i+1]}{renderer},
            attr => $column_types{$_[$i+1]}{attr},
            column_builder => $column_types{$_[$i+1]}{column_builder},
        };
    }

    ## Create the store
    my $model = Gtk3::TreeStore->new (map {$_->{type}} @column_info);
    for (my $i = 0; $i < @column_info ; $i++) {
        if (!defined($column_info[$i]{rtype}) && defined($column_info[
+$i]{column_builder}) && ('CODE' eq ref $column_info[$i]{column_builde
+r})) {
            # A column builder has been defined
            $view->append_column($column_info[$i]{column_builder}());
        }
        elsif ('CODE' eq ref $column_info[$i]{attr})
        {
            $view->insert_column_with_data_func (-1,
                $column_info[$i]{title},
                $column_info[$i]{rtype}->new,
                $column_info[$i]{attr}, $i);
        }
        elsif ('hidden' eq $column_info[$i]{attr})
        {
            # skip hidden column
        }
        else
        {
            my $column = Gtk3::TreeViewColumn->new_with_attributes (
                $column_info[$i]{title},
                $column_info[$i]{rtype}->new,
                $column_info[$i]{attr} => $i,
            );
            $view->append_column ($column);

            if ($column_info[$i]{attr} eq 'active') {
                # make boolean columns respond to editing.
                my $r = $column->get_cells;
                $r->set (activatable => 1);
                $r->signal_connect (toggled => sub {
                    my ($renderer, $row, $col) = @_;
                    my $path = Gtk3::TreePath->new_from_string ($row);
                    my $iter = $model->get_iter ($path);
                    my $val = $model->get ($iter, $col);
                    $model->set ($iter, $col, !$val);
                    }, $i);

            } elsif ($column_info[$i]{attr} eq 'text') {
                # attach a decent 'edited' callback to any
                # columns using a text renderer.  we do NOT
                # turn on editing by default.
                my $r = $column->get_cells;
                $r->{column} = $i;
                $r->signal_connect (edited => \&text_cell_edited,
                            $model);
            }
        }
    }
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