Made an OS/2 Warp 3-ish theme for my X11 window manager and finally added support for showing application icons in the top left corner.
Unfocused windows have a slightly darker border (unlike in OS/2), which helps me identify which window has focus.
(The WM is keyboard-driven only, hence I left out the minimize/maximize buttons in the right corner.)
(Is X11 #RetroComputing yet?)