Step one: Create a new image, with a transparent background or open the document containg the image you want to use. The images that work best are ones that are a flat color, usualy black. Make a duplicate of the first layer. Load the layer selection (Ctrl + click on layer image) and click on the Channels Pallete. Create a new channel and with the selection still active, fill it with white.

Step two: Keeping your selection active, go to Filters > Blur > Gaussian Blur, and put in a value of 9. Click Ok. Then repeat, using values of 7, 5, 3 and 1. This is to make sure that your bevel will look smooth. When you're done with that, invert your selection (Ctrl + Shift + I), and press delete twice, to clear up any inconsistancies. Deselect (Ctrl + D), and go back to the Layers Pallete.

Step three: Highlight the layer with the image and go to Filters > Render > Lighting Effects. Place 2 "Directional Lights" side by side, one should be white pointing up and to the right, and the other should be the color of your choice and pointing down and to the left (as shown in the picture). Both light anchors should be positioned as shown in the caption. Set the slider values as follows:

Intensity: 50 (change this to change the intensity of the light, try not to go too high)
Gloss: 100 (Shiny)
Material: -100 (Plastic)
Exposure: +25
Ambiance: -25

"White is high" should be checkmarked, select the Alpha layer we created earlier and set the height to your liking. I used 35 here.

Step four: Looks kind of funky doesn't it, if it is anything like what I got, you'll have a lot of inconsistancies in the picture you just rendered. Load a selection on your layer and bust out the Gussian Blur tool again. Use a value of 2, that seems to work best in this example.

Step five: And voila! A really nice dragon! Use the Hue/Saturation (Image > Adjust > Hue/Saturation) tool to change the color of the image. Now, the reason I told you to duplicate the layer in the beginning, is because it provides a nice outline underlying the beveled image, if you were to take that out it would look kind of washed out. If you really don't want the underlying black layer, then change the brightness and contrast (Image > Adjust > Brightness/Contrast). If you really want to go all out, use some other effects by duplicating the beveled layer, playing around with it, and setting a blending mode (ex. Overlay, Soft Light, etc.). I suggest you always keep an extra layer of your original image hidden, in case you are to mess up. Thanks and enjoy!