diff --git a/tempest/api/image/base.py b/tempest/api/image/base.py
index 02d391b..c875b2f 100644
--- a/tempest/api/image/base.py
+++ b/tempest/api/image/base.py
@@ -100,7 +100,7 @@
         cls.alt_tenant_id = cls.alt_img_cli.tenant_id
 
     def _create_image(self):
-        image_file = StringIO.StringIO('*' * 1024)
+        image_file = StringIO.StringIO(data_utils.random_bytes())
         resp, image = self.create_image(container_format='bare',
                                         disk_format='raw',
                                         is_public=False,
diff --git a/tempest/api/image/v1/test_images.py b/tempest/api/image/v1/test_images.py
index 8528e42..bf55b89 100644
--- a/tempest/api/image/v1/test_images.py
+++ b/tempest/api/image/v1/test_images.py
@@ -44,7 +44,7 @@
             self.assertEqual(val, body.get('properties')[key])
 
         # Now try uploading an image file
-        image_file = StringIO.StringIO(('*' * 1024))
+        image_file = StringIO.StringIO(data_utils.random_bytes())
         _, body = self.client.update_image(image_id, data=image_file)
         self.assertIn('size', body)
         self.assertEqual(1024, body.get('size'))
@@ -157,7 +157,7 @@
         image. Note that the size of the new image is a random number between
         1024 and 4096
         """
-        image_file = StringIO.StringIO('*' * size)
+        image_file = StringIO.StringIO(data_utils.random_bytes(size))
         name = 'New Standard Image %s' % name
         _, image = cls.create_image(name=name,
                                     container_format=container_format,
@@ -338,10 +338,9 @@
                                disk_format, size):
         """
         Create a new standard image and return the ID of the newly-registered
-        image. Note that the size of the new image is a random number between
-        1024 and 4096
+        image.
         """
-        image_file = StringIO.StringIO('*' * size)
+        image_file = StringIO.StringIO(data_utils.random_bytes(size))
         name = 'New Standard Image %s' % name
         _, image = cls.create_image(name=name,
                                     container_format=container_format,
diff --git a/tempest/api/image/v2/test_images.py b/tempest/api/image/v2/test_images.py
index 4226815..a974ebb 100644
--- a/tempest/api/image/v2/test_images.py
+++ b/tempest/api/image/v2/test_images.py
@@ -52,7 +52,7 @@
         self.assertEqual('queued', body['status'])
 
         # Now try uploading an image file
-        file_content = '*' * 1024
+        file_content = data_utils.random_bytes()
         image_file = StringIO.StringIO(file_content)
         self.client.store_image(image_id, image_file)
 
@@ -104,8 +104,7 @@
         image_id = body['id']
 
         # Now try uploading an image file
-        file_content = '*' * 1024
-        image_file = StringIO.StringIO(file_content)
+        image_file = StringIO.StringIO(data_utils.random_bytes())
         self.client.store_image(image_id, image_file)
 
         # Update Image
@@ -146,7 +145,8 @@
         image. Note that the size of the new image is a random number between
         1024 and 4096
         """
-        image_file = StringIO.StringIO('*' * random.randint(1024, 4096))
+        size = random.randint(1024, 4096)
+        image_file = StringIO.StringIO(data_utils.random_bytes(size))
         name = data_utils.rand_name('image-')
         _, body = cls.create_image(name=name,
                                    container_format=container_format,
diff --git a/tempest/common/utils/data_utils.py b/tempest/common/utils/data_utils.py
index 174e557..5a29ea0 100644
--- a/tempest/common/utils/data_utils.py
+++ b/tempest/common/utils/data_utils.py
@@ -71,3 +71,11 @@
     if not base_text:
         base_text = 'test'
     return ''.join(itertools.islice(itertools.cycle(base_text), size))
+
+
+def random_bytes(size=1024):
+    """
+    Return size randomly selected bytes as a string.
+    """
+    return ''.join([chr(random.randint(0, 255))
+                    for i in range(size)])