Your image can be higher in size but the dimension ratio should be 930px X 354px. So, when your image will have 1940px width, it should be 738px in height. You can also set full width of any images using the following in the WP-Admin > Appearance > Small Business Options > General Options > Custom Code within Head Area Box. But, that will stretch your image. The best way is to maintain the Width and Height Ratio. You can crop the images using image Editor including online tool PIXLR
<style>#slider img { width: 100%; }</style>
You can do such styling using This Technique
