Keep in mind that background will be the vast part of your banner and will play a very important role in the overall perception of the banner by the target viewer. Try not to overload the image with multiple objects, in case you're using one as a background.
Also, try using an image that will fit to the size of the banner, otherwise, it might not retain its original proportions. Unfortunately, neither compressed nor stretched out banner images will be adequately perceived and will not be valued by your visitors.
There are also a few tips in case you will go for solid or gradient color as a background. The major issue is with strong emotional color association, say, a bright red color can often trigger a sense of insecurity or even danger, and the last thing you want is people evading your website. Black is commonly used to display gloom and depression, green is known as a "safe-to-go"-color worldwide and orange normally promotes offbeat types of personalities.
The most motivating, productive and trustworthy color is light-blue. This doesn't mean that banners with a prevailing sky blue background will necessarily secure your success, though it helps to reveal a path to a clear and understandable banner solution.
Major banner objects should have a strong contrast with the background. You should consider these situations when you only have few seconds to attract your visitor.
A mish-mash of rather similar colors can be confusing and, moreover, will lead to slower perception of the message and consequently a negative overall banner experience.
Enhance images before uploading them. Please check if the image size is correct and manually crop any unnecessary image parts if you feel comfortable using an image editor. You can read in our tutorial about most popular editors; more detailed information can be found here.
Sketch out a brief plan of your upcoming work. It will be far more achievable if you visualize and have an understanding of you want to do. Have a look at how may different banner designs look in our Gallery!