You should contact the artist that you used their props. Most artist won't have a problem giving you permission and then you'd know your safe without any doubts. Copyright issues are often fuzzy areas that can usually be cleared up with permission from the original artist. The term "non-commerical" is better defined by calling it "personal use". The moment it's given to someone else it's considered illegal distribution and when it's used in any form to make money (whether you keep the funds or give to a charity) it's a copyright violation.