You can use any Window Manager (WM for short) that has been built for TC. However only some of them support the menu system that TinyCore uses.
From http://forum.tinycorelinux.net/index.php?topic=3283.msg18979#msg18979
- hackedbox
- blackbox
- fluxbox
- openbox
- icewm
- jwm
- jwm-snapshot (451)
all support Tiny Core dynamic application menu.
TC 1.x used jwm by default, http://joewing.net/programs/jwm/ TC 2.x uses flwm by default, http://flwm.sourceforge.net/