At the top of the page with the various locos shown what is the
thing that looks like a yellow shed with stovepipes sticking up?

With the only magnification on me phone, it says "Road of" but can't read the rest... to my untrained eyes it looks like UP colours?

This picture?  I don't know, and I can't remember who sent me the image.

It is a Union Pacific EMD NW2 switcher locomotive. The prototype was first manufactured in 1939.

Here is a picture of a couple of Kato models of it in UP colours.

[smg id=34840 type=preview align=center caption="Kato UP NW2"]

and a photo of the real deal:

[smg id=34841 type=preview align=center caption="A real UP NW2"]

Webbo

Cheers !  Another mystery solved!