[Kasis-anon]

You mentioned that yours was the only chapter that did not yet use a theme as a recruitment tool, may I ask what the other chapters on your campus do for themes? How extensive are their decorations, do they order matching t-shirts or wear other theme-oriented clothing? Do you notice that these themes directly tie into their mascots, mottos etc... If I read your original post correctly you were not yet comfortable with the ideas your fellow members were suggesting, you did not see an immediate connection with Gamma Phi Beta. This might be true, but as you have read party themes are used in recruitment to aid guests in remembering the chapter, as well as for excellent conversation starters within the parties themselves.
Yours is certainly not the only school that holds recruitment in classrooms, you should speak to your advisor and see if they can get in touch with other GPhiB chapters that participate in recruitment within a school or other smaller university buildings.
Also, good luck with the all of the recruitment planning, it is an extremely taxing job no matter what the chapter size, rest assured you are gaining experiences that will serve you in years to come. All of this planning and managing of details is not as "superficial" as some would say. It gives young women major educations in project management. So try and enjoy some of it and know you are doing an amazing thing.