diff --git a/CHANGES.rst b/CHANGES.rst
index 14b4d3a..a4e09e5 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,7 @@
+0.4.2 (2017-10-05)
+------------------
+- Add replace_pic() method to replace pictures from its filename (Thanks to Riccardo Gusmeroli)
+
 0.4.1 (2017-09-10)
 ------------------
 - Improve image attachment for InlineImage ojects
diff --git a/docs/index.rst b/docs/index.rst
index 734ca99..839dccf 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -165,12 +165,29 @@ in your python code ::
 in your docx template just use ``{{ mylisting }}``
 With ``Listing()``, you will keep the current character styling (except after a ``\a`` as you start a new paragraph).
 
-Replace docx medias
--------------------
+Replace docx pictures
+---------------------
 
 It is not possible to dynamically add images in header/footer, but you can change them.
 The idea is to put a dummy picture in your template, render the template as usual, then replace the dummy picture with another one.
 You can do that for all medias at the same time.
+Note: the aspect ratio will be the same as the replaced image
+Note2 : Specify the filename that has been used to insert the image in the docx template (only its basename, not the full path)
+
+Syntax to replace dummy_header_pic.jpg::
+
+   tpl.replace_pic('dummy_header_pic.jpg','header_pic_i_want.jpg')
+
+
+The replacement occurs in headers, footers and the whole document's body.
+
+
+Replace docx medias
+-------------------
+
+It is not possible to dynamically add other medias than images in header/footer, but you can change them.
+The idea is to put a dummy media in your template, render the template as usual, then replace the dummy media with another one.
+You can do that for all medias at the same time.
 Note: for images, the aspect ratio will be the same as the replaced image
 Note2 : it is important to have the source media files as they are required to calculate their CRC to find them in the docx.
 (dummy file name is not important)
@@ -180,8 +197,9 @@ Syntax to replace dummy_header_pic.jpg::
    tpl.replace_media('dummy_header_pic.jpg','header_pic_i_want.jpg')
 
 
-dummy_header_pic.jpg must exist in the template directory when rendering and saving the generated docx. It must be the same
+WARNING : unlike replace_pic() method, dummy_header_pic.jpg MUST exist in the template directory when rendering and saving the generated docx. It must be the same
 file as the one inserted manually in the docx template.
+The replacement occurs in headers, footers and the whole document's body.
 
 Replace embedded objects
 ------------------------
@@ -193,8 +211,9 @@ Syntax to replace embedded_dummy.docx::
    tpl.replace_embedded('embdded_dummy.docx','embdded_docx_i_want.docx')
 
 
-embdded_dummy.docx must exist in the template directory when rendering and saving the generated docx. It must be the same
+WARNING : unlike replace_pic() method, embdded_dummy.docx MUST exist in the template directory when rendering and saving the generated docx. It must be the same
 file as the one inserted manually in the docx template.
+The replacement occurs in headers, footers and the whole document's body.
 
 Jinja custom filters
 --------------------
diff --git a/docxtpl/__init__.py b/docxtpl/__init__.py
index c70fff4..8893356 100644
--- a/docxtpl/__init__.py
+++ b/docxtpl/__init__.py
@@ -5,7 +5,7 @@ Created : 2015-03-12
 @author: Eric Lapouyade
 '''
 
-__version__ = '0.4.1'
+__version__ = '0.4.2'
 
 from lxml import etree
 from docx import Document
@@ -33,7 +33,7 @@ class DocxTemplate(object):
         self.docx = Document(docx)
         self.crc_to_new_media = {}
         self.crc_to_new_embedded = {}
-        self.media_to_replace = {}
+        self.pic_to_replace = {}
 
     def __getattr__(self, name):
         return getattr(self.docx, name)
@@ -213,15 +213,13 @@ class DocxTemplate(object):
 
     def replace_pic(self,embedded_file,dst_file):
         """Replace embedded picture with original-name given by embedded_file.
+           (give only the file basename, not the full path)
            The new picture is given by dst_file.
 
         Notes:
             1) embedded_file and dst_file must have the same extension/format
             2) the aspect ratio will be the same as the replaced image
-            3) There is no need to keep the original file name (compare
-               function replace_embedded).
-
-        Oct 2017 - Riccardo Gusmeroli - riccardo.gusmeroli@polimi.it
+            3) There is no need to keep the original file (this is not the case for replace_embedded and replace_media)
         """
 
         emp_path,emb_ext=os.path.splitext(embedded_file)
@@ -231,7 +229,7 @@ class DocxTemplate(object):
             raise ValueError('replace_pic: extensions must match')
 
         with open(dst_file, 'rb') as fh:
-            self.media_to_replace[embedded_file]=fh.read()
+            self.pic_to_replace[embedded_file]=fh.read()
 
     def replace_embedded(self,src_file,dst_file):
         """Replace one embdded object by another one into a docx
@@ -267,7 +265,7 @@ class DocxTemplate(object):
 
     def pre_processing(self):
 
-        if self.media_to_replace:
+        if self.pic_to_replace:
 
             pic_map={}
 
@@ -281,7 +279,9 @@ class DocxTemplate(object):
                     pic_map.update(self._img_filename_to_part(rel.target_part))
 
             # Do the actual replacement
-            for embedded_file,stream in self.media_to_replace.iteritems():
+            for embedded_file,stream in self.pic_to_replace.iteritems():
+                if embedded_file not in pic_map:
+                    raise ValueError('Picture "%s" not found in the docx template' % embedded_file)
                 pic_map[embedded_file][1]._blob=stream
 
     def _img_filename_to_part(self,doc_part):
diff --git a/tests/replace_picture.py b/tests/replace_picture.py
new file mode 100644
index 0000000..5160b38
--- /dev/null
+++ b/tests/replace_picture.py
@@ -0,0 +1,18 @@
+# -*- coding: utf-8 -*-
+'''
+Created : 2017-09-03
+
+@author: Eric Lapouyade
+'''
+
+from docxtpl import DocxTemplate
+
+DEST_FILE = 'test_files/replace_picture.docx'
+
+tpl=DocxTemplate('test_files/replace_picture_tpl.docx')
+
+context = {}
+
+tpl.replace_pic('python_logo.png','test_files/python.png')
+tpl.render(context)
+tpl.save(DEST_FILE)
\ No newline at end of file
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