Each of the 21 pictures represents the lining of an academic hood worn in a Ph.D. or Masters ceremony. Hood linings represent an academic institution (each institution has a distinctive hood lining - MIT, for instance, is red with a silver-grey chevron).
The flavortext relevant to the puzzle theme is clued by "Doc" (cluing the doctorate and academia) and "my head is cold" (cluing a hood).
Lists or pictures of hood linings are, surprisingly, not present online, thus making the puzzle a little more difficult. An example page of what IS online is here.
Thus the reference materials I used were books. Thanks to Jill Bogard, Director of Library & Information Service of the American Council on Education, and UC Davis librarian Daniel Goldstein.
(Alternatively, I would expect that even in the absence of books, it would not be difficult to start calling up universities and asking what their hood colors are once the universities are narrowed down.)
The next part of the puzzle is to narrow down the list of universities since, for any particular color combination, there are often several universities that correspond to the particular color. (The actual colors used in the 21 pictures have mostly been replicated by visiting the institution's web site and using their university colors.) For example, picture 15 (orange with black chevron) is most often associated with Princeton, but in this case is not Princeton.
The list of potential universities can be narrowed down to the land grant institutions. Each state was given a land grant in exchange for that state establishing a university. About half of these universities have "State" in the name and concentrate on agriculture and engineering. The list I used is here.
The land grant universities were chartered by the Morrill Act of 1862. Googling "1862 colleges" or "1862 universities" has this as the first link:
The land grant schools are clued by "'62" (1862) and "more ill" (Morrill). Googling "moreill 1862" gets you a "Do you mean ..." that gets you to the right place.
The linings chosen for the puzzle are unique among the land grant schools, which have a handful of conflicts. (Florida/Auburn, for example, and Kentucky/Utah State.) The list is below:
The only school with a tartan hood lining in the United States is Carnegie Mellon University, which lines its hoods with Andrew Carnegie's ancestral tartan.
CMU is located in PENNSYLVANIA, the answer to the puzzle.