So I am biased, but I feel that Philosophy goes well with anything, I know of Medicine, Law, Commerce, Engineering, Humanities, Music, Computer Science and Science students that study Philosophy at undergrad level. Also very few people major in it unlike International Relations, which would help you stand out as well as from the fact it's perceived as difficult. The topics and things discussed are really interesting as well, I don't think you will get bored.
If you are interested in the cross-cultural aspect, I would also recommend Anthropology. It's a discipline where you get to explore issues like issues such as social inequality, gender, technology, public health, migration, religion, human rights, climate change, and globalisation in a cross-cultural and observation based manner. The cross-cultural, storytelling and ethnographic aspects would complement marketing especially well (there are also quite a few anthropology-based marketing firms like Flamingo in London or ReD Associates based in Denmark).