>>2244855It's all just pretty basic fvwm theming, I did it myself. It's a bit of a pain but if you read the docs (wiki and manpages) it's not too difficult even for a non-programmer like me. But if you wanted a similar retro look without dumping time into reading manpages I wholeheartedly recommend Icewm, it justwerks and is tied with fvwm for my favorite.
Oh and for the icons in the taskbar (which is also made in fvwm), I just nabbed them from the 16x16 folder of the SE98 icon set.