Pillsbury Hall in 1890 (photo courtesy of University of Minnesota Archives).
The University of Minnesota's Gopher yearbooks for 1893, 1894, and 1897 contained images of Pillsbury Hall's interior, some of which were included in an 1893 Souvenir Manual of the MN Educational Exhibit - World's Columbian Exposition found by Rebecca Toov of the University of Minnesota Archives. That pamphlet also contained the floor plans for Pillsbury Hall at the time although the floor plans labels were nearly illegible.
The image below is a draft composite of the 1893 floor plans with the location and perspective of the Gopher images.
Link to a 7mb version of the composite you can use to see the room images in detail.
The small darker green dot is the apparent location where the photograph was taken, while the lighter green quarter circle shows the direction viewed.
No floor plans of the basement were included, so the lower level photographs are simply labeled east and west ends. In addition, there is sadly only one photograph of the zoological museum on Pillsbury's upper level. It would be wonderful to have more.
Botany's herbarium grew dramatically over this time so in the 1893 photos, it was located in a small room on the upper level. By 1897, the herbarium was so large that it moved to the same room that held the zoological museum and its previous location became the botany library.
Pillsbury Hall 1890s floor plans with photographs of rooms. Lower floor plan is Pillsbury's present middle level, while the upper level's is above. I could not find a contemporaneous floor plan of the building's lower level (then its basement).