I have no interest in learning Adobe Illustrator, but one of the things it is useful for is that it lets you create graphic objects like curves. These are great for customizing borders, or for adding interesting visual elements to print or web-based ads.
Fortunately, Photoshop has many of the same graphic tools. Below is a step-by-step example of how to create a little curved border using the Pen Tool.
Step 1: Open your image and create a new layer.
Step 2: Select the Pen Tool from the toolbar.
Step 3: Click 4 corners outside your image to create a selection path. You don’t have to have exactly straight lines, but if an exact size is necessary, you can drag some guides onto your image before you start.
Step 4: Go back to the Pen tool box (step 2). Just below the Pen Tool, select the Add Anchor Point tool. Click on the bottom line of your selection box at about 1/3 of the way across and 2/3 across to create some anchor points. Photoshop will automatically add additional anchor points, but you can ignore them for now.
Step 5: Hold down your mouse button on one of 2 anchor points you just created and drag it up. Then drag the other anchor point down. You can adjust these until you have a nice curve. As you drag an anchor point, Photoshop puts little handles on them (you can ignore).
Step 6: From the (F7) layers window, select the Paths tab, then select Make Selection. A dialog box will pop up and ask you if you want to feather the edge. Enter a radius, or keep the 0 default. Click OK.
Step 7: Now you’ll have a selection bordered by “marching ants” with a curved edge in a layer. You can fill it with color, stretch it, re-size it, or do anything you want. In this example, I made a copy, filled one layer with blue and the one under it with green. by adjusting the layers with my arrow keys, I got this nice green border.
If you’ve never played with the Pen Tool in Photoshop, I recommend you give it a try. In a few minutes you’ll master the basics, and then be inspired to try lots of different graphic effects.