Ah Ha!! So you wish to know the secret to the corner graphics? Well I guess I can divulge that information. ^_^ Its actually much simpler than you think.

Creating & Using Corner Backgrounds

Step 1:

Choose the image you wish to use. I've chosen this wonderful manga group image.

Step 2:

Decide on what part of the image you want to use for the border. Use the selection tool to select the area you DO NOT want.

Then set your background to white (any colour will do but I'm using white for this tutorial) and cut the part you selected. Notice the border forming already?!

Step 3:

Increase the Canvas Size. Keep the origional height but increase the width to 600 or 700. Be sure you have the Center Image Vertically checked, Center Image Horizontally unchecked and set left to zero. You should end up with this:

Step 4:

Use the Line Tool (foreground colour black) to place a thin black line around the edge of the image and the Airbrush (foreground colour same as background) to create a faded edge look on the top right and the bottom left.

Step 5:

Select the top half, copy it and Paste as New Image. Now under Selections choose Invert and then Crop to Selection. Do the same thing for the side by selecting and croping. Go back to the top half and starting at the top left corner Select it until you reach the width of the side/bottom image. Copy and paste as new image. Then invert the selection on the top and crop to selection. You should now have three images like this:

Here's the basic HTML for using the Corner Backgrounds. Remember to add the with and height to all the images. Notice how I labeled them A, B & C above, thats the order the will be placed in the image.