diff --git a/fluents/fluents.py b/fluents/fluents.py
index 003995b..fe9297e 100644
--- a/fluents/fluents.py
+++ b/fluents/fluents.py
@@ -22,6 +22,27 @@ DATADIR = os.path.dirname(sys.modules['fluents'].__file__)
 ICONDIR = os.path.join(DATADIR,"..","icons")
 GLADEFILENAME = os.path.join(DATADIR, 'fluents.glade')
 
+class IconFactory:
+    """Factory for icons that ensures that each icon is only loaded once."""
+
+    def __init__(self, path):
+        self._path = path
+        self._icons = {}
+
+    def get_icon(self, iconname):
+        """Returns the gdk loaded PixBuf for the given icon.
+        Reads the icon from file if necessary."""
+
+        if self._icons.has_key(iconname):
+            return self._icons[iconname]
+
+        icon_fname = os.path.join(self._path, '%s.png' % iconname)
+        icon = gtk.gdk.pixbuf_new_from_file(icon_fname)
+        self._icons[iconname] = icon
+        return icon
+
+icon_factory = IconFactory(ICONDIR)
+
 class TableSizeSelection(gtk.Window):
     
     def __init__(self):
diff --git a/fluents/project.py b/fluents/project.py
index fa5cecb..9eadfc3 100644
--- a/fluents/project.py
+++ b/fluents/project.py
@@ -67,32 +67,32 @@ class Project:
         else:
             parent_iter = None
 
-        icon_fname = os.path.join(fluents.ICONDIR, "folder_grey.png")
-        icon = gtk.gdk.pixbuf_new_from_file(icon_fname)
+        # Add the function node to the tree
+        icon = fluents.icon_factory.get_icon("folder_grey")
         it = self.data_tree_insert(parent_iter, fun, None, None, "black", icon)
         
+        # Add all returned datasets/plots/selections
         for d in data:
-            if isinstance(d, dataset.GraphDataset):
+            # Any kind of dataset
+            if isinstance(d, dataset.Dataset):
+                if isinstance(d, dataset.GraphDataset):
+                    icon = fluents.icon_factory.get_icon("graph_dataset")
+                elif isinstance(d, dataset.CategoryDataset):
+                    icon = fluents.icon_factory.get_icon("category_dataset")
+                else:
+                    icon = fluents.icon_factory.get_icon("dataset")
+
                 self.add_dataset(d)
-                icon_fname = os.path.join(fluents.ICONDIR, "graph_dataset.png")
-                icon = gtk.gdk.pixbuf_new_from_file(icon_fname)
-                self.data_tree_insert(it, d.get_name(), d, None, "black",icon)
-            elif isinstance(d,dataset.CategoryDataset):
-                icon_fname = os.path.join(fluents.ICONDIR,"category_dataset.png")
-                icon = gtk.gdk.pixbuf_new_from_file(icon_fname)
-                self.add_dataset(d)
-                self.data_tree_insert(it, d.get_name(), d, None, "black",icon)
-            elif isinstance(d, dataset.Dataset):
-                icon_fname = os.path.join(fluents.ICONDIR,"dataset.png")
-                icon = gtk.gdk.pixbuf_new_from_file(icon_fname)
-                self.add_dataset(d)
-                self.data_tree_insert(it, d.get_name(), d, None, "black",icon)
+                self.data_tree_insert(it, d.get_name(), d, None, "black", icon) 
+
+            # Any kind of plot
             elif isinstance(d, plots.Plot):
-                icon_fname = os.path.join(fluents.ICONDIR,"line_plot.png")
-                icon = gtk.gdk.pixbuf_new_from_file(icon_fname)
-                self.data_tree_insert(it, d.get_title(), d, None, "black",icon)
+                icon = fluents.icon_factory.get_icon("line_plot")
+                self.data_tree_insert(it, d.get_title(), d, None, "black", icon)
                 d.set_selection_listener(self.set_selection)
                 self._selection_observers.append(d)
+
+            # Selections are not added to the data tree
             elif isinstance(d, dataset.Selection):
                 self.add_selection(d)