Now this feature would be great for web as well, e.g. responsive design pages. To achieve this we can use the CSS3 feature border-image which combines border-image-source, border-image-width, border-image-slice and border-image-outset.
border-image-source defines which image to use.
border-image-width defines the width of the border image. Stretches or shrinks the image regions to fit the widths.
border-image-slice divides the image into 9 regions, thereby the name (see the image above) deciding which parts can be repeated/stretched. The regions are: four corners, four edges and a middle. The fill property decides if the middle should be filled in or kept transparent.
border-image-outset decides how far out from the border the image will appear. Together with border-width this enables the border to not take up all the space inside the container caused by it having a wide border to fit the image inside (See http://www.norabrowndesign.com/css-experiments/border-image-frame.html#one). This is especially great for select/dropdown boxes as they can't work around this by using line-height (http://stackoverflow.com/questions/18613279/text-over-the-top-of-a-border-image-using-the-border-as-an-expandable-backgroun)
border-image combines the four above properties, but I felt I had more control when splitting them up. However, as of right now browser support for border-image and especially border-image-outset is a bit limited. Most browsers support border-image, but might need browser-specific CSS (e.g. -webkit-border-image).
border-image-width: 25% 10% 25% 5%;
border-image-slice: 10 70 20 60 fill;
http://border-image.com lets you generate border-image CSS from an image. but it doesn't put in border-image-outset.