Trademark infringement is bad stuff. If you are infringing on another party's mark then at best you have to give up all the work you put into building that brand. At worst you get sued and the court orders you to give up the infringing content plus you pay their attorney fees and your own.
A search of the USPTO trademark database should be your starting point but it's not the only search you should do. You should also search your state's mark database if your state provides trademark registration (as I think all do) as well as a basic internet search. Trademarks do not have to be registered with federal or state offices. They can be protected under common law rights. Your search should be for both images and names.
USPTO will supersede any state trademarks. You need to have federal trademark.
I'm my state you can register the mark for informational info only. So why bother.
I could disagree that you do not have to register trademark. If you do not do it, you do not have trademark. You could try Prior Use but you might not be that lucky.
As I said. I am not a lawyer.