I got to thinking, "Why not put these somewhere in Vvardenfell? Giant mushrooms aren't out of the norm there!". However, I have run into a dilemma:
Which giant mushroom should they replace? I don't want to mass-edit huge areas of the map populating it with new ones, and I don't want to make it too different from the shape of the original. The Azura's Coast smaller red/orange mushrooms seem to be a better candidate. Alternatively, they could replace a normal tree model, to give the island even more shroom-age. However, I am ridiculously horrible at making decisions, so I leave it up to you.
Here's a close up of one of the models: http://i43.tinypic.com/2rgcrpl.jpg
(Textures are partially from a friend's photo archive, and partially hand-painted)