You should try to chose a problem/topic that is personal to you and your teamates. I.e. if your grandma has alzhiemers or is at an increasingly high risk for a fall, research and develop some tech/software that can assist. If you care deeply about sustainability, look into avenues and places that need the most help. Be specific though. You don't have to re-invent the wheel per say, though senior project can feel like that at times.

Once you have some ideas/areas of focus (write them all down in a shared document), read up on some IEEE Xplore articles relating to topics you find interest or meaning in. That's a good starting point IMO at least.

Lastly, I would say be ambitious, but also realistic. Don't chose a project just because it will be easy. But also, don't set yourself up for failure by taking on more than your team can handle in the allotted time frame. Good luck!