Having images is on your website is a great way to break the page up, as well as making it look better. Having the right image(s) on your website will either make or break it; for example the image you have chosen could be a good image, but if it neither backs up what the website is saying, or serves no purpose to the website, then it is useless and makes the whole site look unprofessional.
The first thing to consider when choosing an image is relevance. It can be argued that having an image on the page will make it more visually appealing, but if it’s relevant to the surrounding context it will look much better. To put this into perspective, imagine a website for a farm, if the home page has a stock image of a stereotypical businessman sat behind a desk wearing a suit drinking coffee, it will both look horrible, and serve no purpose. A more relevant image, such as a pig, will look better and serve a better purpose for the website.
Another important factor to consider is the file type that the image is saved as. Some file types have certain advantages over others when it comes to being put on the web. .jpeg file type is always a safe option to go for, as they are highly compatible and fairly small in size. Another good file type to look use for the web are .png files, as .png images allow for transparent backgrounds which will make your website look professional. Your website will also look more natural, plus, .png files are very small is size compared to other file types.
It is also extremely important to think about who owns the image you are using. Using images that you have taken or created yourself is absolutely fine, but using an image straight off a search engine could land you in some trouble in the long run. Make sure if you’re going to use an image from an external source that you have the correct permission!
A final factor to consider is size. This means both the size of the image on the web page itself, and the size of the actual image. If the image you’re using is a small image (for example, 50 pixels by 50 pixels), making it any larger will cause it to become distorted. This is because images cannot be enlarged without losing quality, where as they can be shrunk without losing quality. It is always a good idea to use an image a little bit too big for this reason. With respect to how physically big the image is on the website itself, it again depends on relevance. Some websites will benefit from having small images (more text based pages), whereas some will look better with large images (these are typically more modern, arty websites).
To wrap things up, having images is important on your website, but they must be relevant and they must be your photos, or you must have permission to use the image. The size of image is also important, have it too large and it could be distracting and lose quality, or have it too small and it'll be unnoticeable and have less of an impact that you desire.