Personally I use Pixlr. its a good starting editor AND its a browser (no download required). There are better editors out there but this one is free and beginner friendly. If your making thumbnails on the go, I recommend using BAZAART (its a mobile app)
Sorry brother Idk, I believe you have to register for a license through a subscription thing. I never looked into it so I could be wrongI just checked out Pixlr as you suggested. It is an excellent suggestion for someone who wants "free". Some nice thumbnail templates.
It is pretty cool and also has some nice free thumbnail templates. The background remover feature is separate from the main editor but it is free.
Do you happen to know the licensing policy of the images they offer?