If the covers in your genre's section of the bookstore are all orange, should your cover be orange, too? It's hard to say. You want it to look like it belongs in that section, right? But you also want it to stand out. I would say, if you are a new author and you are predominantly selling online, you need to consider how your work is going to look when it's shown with others in the genre.
The biggest and most measurable benefit is that it keeps you writing. You can often spark creativity by simply being creative, that is, you write five or seven days per week, and you can fill up that writing time fairly readily. But if you only write three times per month, you may find you have writers' block when you make the infrequent attempt. There is something about the pressure of deadlines or at least the pressure of your own internal expectations. It helps to not have a blank page to stare at all the time.
Never, ever use the word 'by' unless you are referring to an 'edited by' line. Otherwise, just use your name as the author name. Don't believe me? Go to a bookstore or Amazon and look at what's out there.
Just because you can right-click an image or take a screenshot does not mean you have the right to just take it. And do not get me started on wiping off someone else's photographic watermark. Just don't do it. Don't be a jerk.