A Windows 3.x UI theme would get the childhood nostalgia going much stronger for me than a 95/NT4/98/2000/Me theme does.
Occasionally I boot up Windows 3.1 in a VM and play a game of Solitaire, for old time’s sake - I can run Windows 95 in a VM too, but it just doesn’t have the same pull.
Win3.1 works great in DOSBox, and you can get an even more authentic '80s-'90s IBM-compatible experience using PCEm or 86box, which emulate a wide variety of PC motherboards, graphics cards, and sound cards.
Occasionally I boot up Windows 3.1 in a VM and play a game of Solitaire, for old time’s sake - I can run Windows 95 in a VM too, but it just doesn’t have the same pull.