It is completely dependent to your skills and relations with well-known companies for getting datasets. should I know more about your ability,appropriate guidance can be provided by me.
Several domains are still open in Machine Learning (ML). It totally depends on your skills. You can apply the already existing ML algorithms in Image fusion (Image processing), Wireless Communication Security, Pattern Recognition, Computer vision, etc. However, you can also propose a novel ML algorithm for the aforementioned domains.
You can refer to the following link for more details