If China entered the war on the Entente side (the saner choice, in my view) it could have contributed labor and supplies and been an early member of the League of Nations. It's contributions though would have come too late and would have been too small for it to be a permanent League Council member though.
And, I think that for China to get Qingdao instead of Japan (and thus averting full-scale Sino-Japanese war in the late 1920s), Yuan Shikai would have had to move instantly. After November 1914, Japan's Qingdao leasehold was going to be a fact of life for the next 20 years, as the Japanese had "conquered it fair and square" from the Germans, and possession is 9/10ths of the law.
If China entered on the Central Powers side, it would be Boxer Rebellion # II. The Chinese would not have distracted first-line Entente troops from anything more important in Europe, and Japan would have been given carte blanche to beat down China. Japan might have gotten League of Nations mandates over Manchuria and Shandong and Inner Mongolia or more. Britain might have gotten a mandate over Tibet. Only revolution in Russia (don't see why that would change) would prevent Russian mandates in Sinkiang, outer Mongolia and northern Manchuria. Perhaps even a French mandate over Yunnan and Kwangsi provinces in China's southwest.
Worst of all for China might have been if "China" joined *both* sides. There would have been a real risk of the Canton regime of Sun Yat-sen joining the CP if the Beiyang regime joined the Entente, or vice versa. Sun was a rabble-rouser determined to bring down Beiyang and to work with absolutely anyone to do it.