Here's AmigaOS 1.x:

http://www.gregdonner.org/workbench/wb_13.html

(2.x went bevelled, and none of us looked back)

Whoa! That brings back memories. Even more than the NeWS interface I brought up on one of our Suns recently, just for fun.

It always bothered me, that the colors of twm are so ugly.

Here is a recolored screenshot using the UI colors cited above: http://oi60.tinypic.com/140yiqr.jpg

Now it only needs some font aliasing and it is fit for a revival.

I know you posted tongue in cheek, but that's genuinely not that bad with nice colours

The Jabberwock, with eyes of flame...

“Remember”? I still use it.

My memory (admittedly, ropey) of Windows 95 is that it was very, very 'unflat' - e.g. the start menu alone was a hefty, three-dimensional button.

Seriously. It's like scaling Mt. Everest to get to the program you want to launch: http://www.guidebookgallery.org/pics/gui/desktop/full/win95....

You don't have to be older. twm is available on FreeBSD and I'm sure it can be installed on Linux.

I do not understand. The first screenshot has nothing to do with flat design for me. There are reliefs, shadings, etc.