Image and media files in general tend to be the largest component of file size on most modern webpages. File size can directly impact how quickly a page loads, and subsequently the quality of the experience for users. Images in general can have a large range in how much they can be optimized. For example, a high quality photograph downloaded from a camera could be 16MB, but using a reasonable level of size reduction and optimization could comfortably reduce it to 150KB without a noticeable amount of quality loss.
Review the images used on your site, starting from the largest in file size to determine if there are optimization opportunities. You can use common image editing tools like Photoshop or even free online compression tools to optimize them.