diff --git a/uploadr.py b/uploadr.py
index 263bc5ff..db84d97f 100755
--- a/uploadr.py
+++ b/uploadr.py
@@ -65,13 +65,26 @@
 import json
 from xml.dom.minidom import parse
 import hashlib
-import fcntl
 import errno
 import subprocess
 import re
 import ConfigParser
 from multiprocessing.pool import ThreadPool
 
+try:
+    # fcntl module only available in linux/unix platforms
+    import fcntl
+except ImportError:
+    sys.stderr.write('No fcntl module available. Skipping multiple instances check.')
+
+try:
+    # Try to import a module used to check if the files are valid image files
+    from PIL import Image
+    chkImages = True
+except ImportError:
+    sys.stderr.write('Image module not available. Not checking is image files are valid.\n')
+    chkImages = False
+
 if sys.version_info < (2, 7):
     sys.stderr.write("This script requires Python 2.7 or newer.\n")
     sys.stderr.write("Current version: " + sys.version + "\n")
@@ -455,10 +468,29 @@ def grabNewFiles(self):
                 if ext in ALLOWED_EXT:
                     fileSize = os.path.getsize(dirpath + "/" + f)
                     if (fileSize < FILE_MAX_SIZE):
-                        files.append(os.path.normpath(dirpath + "/" + f).replace("'", "\'"))
+                        # add check if file has valid image
+                        if isValidImageFile(dirpath + "/" + f):
+                            files.append(os.path.normpath(dirpath + "/" + f).replace("'", "\'"))
+                        else:
+                            print '   ! Skipping invalid file %s' % (dirpath + "/" + f)
         files.sort()
         return files
 
+    def isValidImageFile(self, ffname):
+        """check if image file is a valid image file
+        """
+        if not chkImages:
+            return True
+        try:
+            fd = open(ffname, 'rb')
+            im = Image.open(fd)
+            im.verify()
+            fd.close()
+            return True
+        except IOError:
+            fd.close()
+            return False
+
     def uploadFile(self, file):
         """ uploadFile
         """
@@ -1125,6 +1157,8 @@ def print_stat(self):
     f = open(LOCK_PATH, 'w')
     try:
         fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
+    except NameError:
+        pass
     except IOError, e:
         if e.errno == errno.EAGAIN:
             sys.stderr.write('[%s] Script already running.\n' % time.strftime('%c'))