Hmm, tricky one. Can only speak for the arts I know well (IMA). For xingyiquan, oldest photo is probably the famous photo of Guo Yunshen visiting Che Yizhai in Taigu in 1903 - but they're seated, not actually showing any xyq. Oldest set of photos of actual xingyiquan and baguazhang practice are probably Sun Lutang's books, 'Baguazhang Xue' （the study of bgz) and 'Xingyiquan Xue' (the study of xyq), which were published in 1915-16. This period (~1915 - 1930s) saw a lot of books published in TCMA, by masters like Huang Bonian, Jiang Rongqiao, Xue Dian, Yin Fu's son Yin Yuzhang, etc etc. For taiji the earliest pictures are probably of Yang Chengfu from Chen Weiming's book, Taijiquan Shu (the art of tjq), published in 1925.
Video would be (much) later, depending on which art. Earliest video I can think of is of Wu Jianquan's student Chu Minyi, which was shot in the 1930s.