diff --git a/icons/ebook-edit.ico b/icons/ebook-edit.ico
index e499af829a..6c850dbd82 100644
Binary files a/icons/ebook-edit.ico and b/icons/ebook-edit.ico differ
diff --git a/icons/favicon.ico b/icons/favicon.ico
index b8b7c1fd5e..892dc7ec00 100644
Binary files a/icons/favicon.ico and b/icons/favicon.ico differ
diff --git a/icons/library.ico b/icons/library.ico
index b8b7c1fd5e..892dc7ec00 100644
Binary files a/icons/library.ico and b/icons/library.ico differ
diff --git a/icons/make_ico_files.py b/icons/make_ico_files.py
index 8f1fc2fe7e..c7e7423a70 100644
--- a/icons/make_ico_files.py
+++ b/icons/make_ico_files.py
@@ -19,12 +19,15 @@ for name, src in sources.iteritems():
     os.mkdir('ico_temp')
     try:
         names = []
-        for sz in (16, 32, 48, 256):
+        for sz in (16, 24, 32, 48, 64, 256):
             iname = os.path.join('ico_temp', '{0}x{0}.png'.format(sz))
             subprocess.check_call(['rsvg-convert', src, '-w', str(sz), '-h', str(sz), '-o', iname])
             subprocess.check_call(['optipng', '-o7', '-strip', 'all', iname])
+            if sz >= 128:
+                names.append('-r')  # store as raw PNG to reduce size
+            else:
+                names.extend(['-t', '0'])  # see https://bugzilla.gnome.org/show_bug.cgi?id=755200
             names.append(iname)
-        names[-1:-1] = ['-r']
         subprocess.check_call(['icotool', '-c', '--output=' + name+'.ico'] + names)
     finally:
         shutil.rmtree('ico_temp')
diff --git a/icons/viewer.ico b/icons/viewer.ico
index a4599ba598..7f229f9643 100644
Binary files a/icons/viewer.ico and b/icons/viewer.ico differ
diff --git a/src/calibre/gui2/main.py b/src/calibre/gui2/main.py
index 0c84a66d14..9349511240 100644
--- a/src/calibre/gui2/main.py
+++ b/src/calibre/gui2/main.py
@@ -100,7 +100,7 @@ def init_qt(args):
     override = 'calibre-gui' if islinux else None
     app = Application(args, override_program_name=override)
     app.file_event_hook = EventAccumulator()
-    app.setWindowIcon(QIcon(I('lt.png', allow_user_override=False)))
+    app.setWindowIcon(QIcon(I('library.png', allow_user_override=False)))
     return app, opts, args
 
 
@@ -462,6 +462,16 @@ def main(args=sys.argv):
         gui_debug = args[1]
         args = ['calibre']
 
+    if iswindows:
+        # Ensure that all ebook editor instances are grouped together in the task
+        # bar. This prevents them from being grouped with viewer process when
+        # launched from within calibre, as both use calibre-parallel.exe
+        import ctypes
+        try:
+            ctypes.windll.shell32.SetCurrentProcessExplicitAppUserModelID('com.calibre-ebook.main-gui')
+        except Exception:
+            pass  # Only available on windows 7 and newer
+
     try:
         app, opts, args = init_qt(args)
     except AbortInit:
diff --git a/src/calibre/gui2/tweak_book/main.py b/src/calibre/gui2/tweak_book/main.py
index fed5d43e20..535a8b0502 100644
--- a/src/calibre/gui2/tweak_book/main.py
+++ b/src/calibre/gui2/tweak_book/main.py
@@ -48,7 +48,7 @@ def _run(args, notify=None):
         import ctypes
         try:
             ctypes.windll.shell32.SetCurrentProcessExplicitAppUserModelID('com.calibre-ebook.edit-book')
-        except:
+        except Exception:
             pass  # Only available on windows 7 and newer
 
     # The following two lines are needed to prevent circular imports causing
diff --git a/src/calibre/gui2/ui.py b/src/calibre/gui2/ui.py
index 6a83ea11a4..1335846de3 100644
--- a/src/calibre/gui2/ui.py
+++ b/src/calibre/gui2/ui.py
@@ -134,6 +134,7 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin,  # {{{
     def __init__(self, opts, parent=None, gui_debug=None):
         global _gui
         MainWindow.__init__(self, opts, parent=parent, disable_automatic_gc=True)
+        self.setWindowIcon(QIcon(I('library.png', allow_user_override=False)))
         self.jobs_pointer = Pointer(self)
         self.proceed_requested.connect(self.do_proceed,
                 type=Qt.QueuedConnection)
diff --git a/src/calibre/gui2/viewer/main.py b/src/calibre/gui2/viewer/main.py
index 7ebc95fd45..37a1bec7ff 100644
--- a/src/calibre/gui2/viewer/main.py
+++ b/src/calibre/gui2/viewer/main.py
@@ -16,7 +16,7 @@ from calibre.gui2 import (
     Application, ORG_NAME, APP_UID, choose_files, info_dialog, error_dialog,
     open_url, setup_gui_option_parser)
 from calibre.ebooks.oeb.iterator.book import EbookIterator
-from calibre.constants import islinux, filesystem_encoding, DEBUG
+from calibre.constants import islinux, filesystem_encoding, DEBUG, iswindows
 from calibre.utils.config import Config, StringConfig, JSONConfig
 from calibre.customize.ui import available_input_formats
 from calibre import as_unicode, force_unicode, isbytestring, prints
@@ -1207,6 +1207,15 @@ def main(args=sys.argv):
     # Ensure viewer can continue to function if GUI is closed
     os.environ.pop('CALIBRE_WORKER_TEMP_DIR', None)
     reset_base_dir()
+    if iswindows:
+        # Ensure that all ebook editor instances are grouped together in the task
+        # bar. This prevents them from being grouped with viewer process when
+        # launched from within calibre, as both use calibre-parallel.exe
+        import ctypes
+        try:
+            ctypes.windll.shell32.SetCurrentProcessExplicitAppUserModelID('com.calibre-ebook.viewer')
+        except Exception:
+            pass  # Only available on windows 7 and newer
 
     parser = option_parser()
     opts, args = parser.parse_args(args)