Canva (Canva.com) is by far, the best FREE Design tool I've used. Their site is so easy to navigate and will help anyone end up with a professional graphic. These graphics can be used for website headers /banners, facebook (and other social media posts) and even flyers or email marketing.
Pros:
-FREE & EASY to Use
-Built in templates and design sizes
-Professional Stock photography from just $1 (no costly subscriptions)
Cons:
-You may need to have a bit of vision for what you want the final design to look like.
Again, this is not Fiverr where someone else does the work for you. You can do it yourself, even without knowledge of how to operate design software. Yet if you know what you want, Canva will make it Free, easy and Fast to get your design created.