There are plenty of desktop environments available for Linux now. But I like looking at old ones from time to time. Here is the GitHub of AmiWM. This might be a more recent repository. The benefit of using a nice WM like this is the interface’s speed compared to Gnome and KDE. It is able to be personalized and customized with various other programs like Xeyes, Xload and a couple of terminals open. That is all you need sometimes. Window Maker is another alternative for the Linux desktop. This is modelled after the NextStep desktop interface and has many handy applets with varying functionality and usefulness. Here is a very nice listing of Window Maker applets: http://www.cs.mun.ca/~gstarkes/wmaker/dockapps/sys.html. This page has a large repository of Window Maker themes. For fans of the NeXTSTEP UNIX desktop, there is a Github repos with a version of this desktop for Linux. This would be a very interesting desktop to run, for fans of the original NeXT OS look and feel. The original Doom game was developed on a NeXT machine. And then the source code for Linux was released.
Here is a collection of more WindowMaker themes: http://www.cs.mun.ca/~gstarkes/wmaker/themes/.
The official WindowMaker home page: http://www.windowmaker.org/.
NeXTSTEP release 3 demonstrations on Youtube. Steve Jobs demonstrates the features of the new operating system.