Fluxbox Macos theme
Original Author: Onur Aslan, http://gitorious.org/fluxbox-macos.
You can download the theme and put them into ~/.fluxbox/styles, then right click the desktop to choose it.
I customized it for my needs. If you want to have a complete Macos-style, you should install one Mac OS style gtk theme(placed in ~/.themes), which you can search on http://gnome-look.org. Then use gnome-tweak-tool or the following command to apply theme:
gsettings set org.gnome.desktop.interface gtk-theme 'gtk-theme-name'
More Fluxbox theme on http://tenr.de/styles/.