include more serious examples of gtk applications
While it's great to mention the default GNOME applications, these are mostly small utilities (Fonts, Calculator, Dictionary, etc). People outside of GNOME world will take GTK much more seriously if they see examples of serious applications that use GTK. I see only GIMP and Glade included. I'm thinking of applications like Inkscape (which just had a GTK3 release), GNOME Builder, Pitivi, Geary, Evolution, as well as other non-GNOME projects like Firefox, Chromium, Audacity, Horizon, Homebank, Darktable. Even GTK apps like Unity3D should be included, despite the fact they don't look "GNOMEish."
Some of the apps I mentioned are from this list: https://github.com/myfreeweb/awesome-gtk