Not only the stadium, but you could argue that "Fighting Illini" was first used in fundraising campaigns for Memorial Stadium.
Where did the term "Fighting Illini" come from?
The best evidence suggests that it was developed and then used extensively as part of the fundraising campaign preceeding the construction of Memorial Stadium.
"An article (jpeg, 453 KB, click image to enlarge, then see third column) from the Illinois Alumni News (April 1925, p. 221) regarding the stadium reads in part: "How the stadium idea, when it started some years ago, did possess the imagination of us all! It was a slow day indeed whose setting sun did not mark another period of slogans. Everybody composed them, especially during a prize contest that was held. Out of this came the battle cry of the stadium campaign: "Build that stadium for fighting Illini." Since the stadium was built to honor alumni, staff, and students who who died during World War I, the term "Fighting Illini" was seemingly being linked to military service. At the same time, the term was broad enough to be of general applicability."
http://archives.library.illinois.edu/features/illini.php
The university could invite "fighting Illini", alumni who have served in the armed forces, to be sideline guests, honored at halftime and lead us in Illinois Loyalty.