What do you think about people in a cover image?

I think I prefer a neutral image without them.

I would say it depends on your product. Most of the time I woul use people in images but in a different context -> group of people representing a "community". I used it for a tool I used to build some time ago ( tool that would deal with facebook groups ).

Well I'm making (work in progress!) So not sure whether to have an image of tropical beach etc or a person

Personally I think it can look good when done well. The caveat being that many images with people in them can look very stock photo-ish. So if you have nice pictures that look natural (e.g. that works!

Yeah someone has offered me Adobe pics. But my competitors use landscape pics so might just go with that ( it's hard to have cheesy person pics)