IceWM is a window manager that controls the appearance, placement and manipulation of windows. It also provides a taskbar. The goal of IceWM is speed, simplicity, and not getting in the user's way. It is a light window manager which should feel familiar to new Puppy users. For advanced users, IceWM is also highly configurable. There are many themes available, which can change the appearance of IceWM to suit anyone's taste. See below for some examples.
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Some of the different window appearances possible using different themes
Some recent puppies come with IceWM pre-installed, although you may have to select it in the window manager selection tool first. Otherwise IceWM may be installed from the package manager. If you must have the latest version a search on the forum can help you locate a recent .pet file.
This is the place where Puppy users are showing off their IceWM installs and sharing themes.
IceWM Themes Exchange
Puppy wiki page about window managers
IceWM home page