diff --git a/docs/design/design-4.html b/docs/design/design-4.html
index 4a3061819..a5829bb54 100644
--- a/docs/design/design-4.html
+++ b/docs/design/design-4.html
@@ -291,7 +291,7 @@
     graph of FreeType&nbsp;2's base design:</p>
 
     <center>
-      <img alt="to be done">
+      <img alt="Library Model" src="library-model.png" width=411 height=405>
     </center>
 
 </td></tr>
diff --git a/docs/design/library-model.png b/docs/design/library-model.png
new file mode 100644
index 000000000..b305458c2
Binary files /dev/null and b/docs/design/library-model.png differ