Fairly simple but effective web site header made with 2 images painted with sea-green gradient and stripes.

A special Rounded Corners Mask images generator module (top-right side of the screen at OGIM engine) is capable of generating nearly perfect round corner images with radius anywhere from 1 to 500 pixels. Generator uses "Antialiasing" and "Matting" to smooth the oval and blend it with the surrounding background color and inner box color or even a pattern. 3 types of masks could be generated: 1) solid 2) with transparent outer oval area 3) with transparent inner oval area. Click "Help" button at OGIM screen or at the top menu for more information.

Here is a sample of the box with striped gradient pattern for the background and corners masked by images generated with OGIM. Note: There is no reference to corner mask images. They are built and downloaded directly at OGIM engine screen. Reference to Orange background pattern.

Another sample of the box with striped horizontal gradient pattern for the background and corners masked by images generated with OGIM. Reference to background pattern.

Following examples demonstrate how to create a bordered rounded and straight corner box with OGIM. This method does not use Masked Corner images but rather gradient images to create line or gradient border. Round corner images are generated with radial gradient. Five images are used to create the box below. Single Image (20x20 px) for round corners was created by using "radial" gradient while rendering a circle. Four remaining images (1x10 px. and 10x1 px.) are created with "line" gradient using the same set of gradient colors respectively configured as horizontal, vertical, mirrored horizontal and mirrored vertical gradients and bound to each side of the box.

Positioning created images for the precise joints is now just a matter of HTML styling. Based on this sample, various round corner and straight cut corner (use "diamond" gradient instead of "radial") boxes could be created with just a little effort and a bit of creativity.
Rounded Corner Box Images Reference: Corner | Left | Right | Top | Bottom

The rounded corners box could be somewhat "raised" as per example below which uses the same method as above but slightly different gradient color points.
Raised Round Corner Box Images Reference: Corner | Left | Right | Top | Bottom

Next example displays a box with raised border on a dark background.
Raised Round Corner Box Images Reference: Corner | Left | Right | Top | Bottom

Another variation with straight corner and line gradient for the middle part. Straight corner is rendered with a rectangle type of gradient.
Straight Corner Box Images Reference: Corner | Left | Right | Top | Bottom | Middle

Classic 8 image slices box with round corners, border and a shadow. Unlike samples above this box is created from a single image sliced with OGIM slicer tool. Reference for the image
After navigating to this OGIM reference, click "More" button within Slicer section, specify width/height for each slice and download 8 images (4 corners, 4 sides).
1 - 8x8 px, 2 - 12x8 px, 3 - 8x12 px, 4 - 12x12 px
5 - 1x8 px, 6 - 1x12 px, 7 - 8x1 px, 8 - 12x1 px
Slices dimension may highly depend on your HTML box styling and overall box configuration (round corner radius, shadow amount .. ect).