What are some alternatives?
When comparing i3 and IceWM, you can also consider the following products
awesome - A dynamic window manager for the X Window System developed in the C and Lua programming languages.
Fluxbox - Fluxbox is a window manager for X that was based on the Blackbox 0.61.1 code.
dwm - dwm is a dynamic window manager for X. It manages windows in tiled, monocle and floating layouts. All of the layouts can be applied dynamically, optimising the environment for the application in use and the task performed.
bspwm - A tiling window manager based on binary space partitioning
Xmonad - xmonad is a dynamically tiling X11 window manager that is written and configured in Haskell.
KWin - KWin is a window manager for the X Window System, and is in the process of becoming a Wayland...