How to design a creative website banner

To design a creative website banner, look around you and look for objects or scenes that might be related to the theme of your website.

If you don’t see anything like this, look around you for objects or scenes which you find interesting and which you think your visitors might find interesting.
The first option - where the image is related to the theme of your website or blog - is probably preferable. The problem with this option is, how `related’ does it have to be? Very related, fairly related or you need a vivid imagination and\or a microscope to see that it’s related?

Banners and visitors

The banner for this website or blog is probably very related. It’s obviously an image of a line of keys on a computer keyboard.
Keyboards are very related to freelance writing because they are used by freelance writers to create freelance writing. They are a direct link between the writer’s ideas and what appears on the screen.
More importantly, most visitors probably accept that keyboards are very related to freelance writing.
An image of a keyboard might even project an image of relevance. Visitors might reason - quite correctly if I may boast a little - that this site is definitely about freelance writing. This might re-assure them, might make them feel comfortable with the site.

Banners and visitors’ interest

Whether it complies with the second option - whether visitors find it interesting, is a matter of opinion.
Let’s face it, a line of keys on a keyboard isn’t very interesting. But it’s unusual to see a photograph of a line of keyboards on a keyboard. So here we have the situation whereby the subject of the banner isn’t very interesting but the way this subject has been handled might be interesting.
To sum it up, this banner probably scores high on option 1 - for relevance to the website or blog, and probably has a medium score on option 2 - on whether visitors find the banner interesting.