Can I use the images made in this program in commercial projects after purchase?

I believe so, I think that was why object import was added. The author is certainly aware that people were thinking of doing this and I don't recall anything being said against it.

According to this thread where the developer provided the answer, you can do whatever you'd like with what you create using FlowScape.  :)  https://itch.io/t/805388/commercial-license-request