Making a Letterseal

Create a new layer, 1000x1000 pixels, black background.

Make a new layer. Using the elliptical marquee tool, draw a large circle in the middle of the layer and fill it with white. With a white paintbrush, draw on the same layer the form of the future seal; here is mine:

Duplicate the layer and with the seal form selected (CTRL+click on the thumbnail of the layer) fill it with a red color (I used #840000).

With the selection active, go to the channels tab and click on the button at the bottom of the channels palette (Save selection as channel).

Ctrl-click the channel and take the Airbrush Tool. Start painting shades of gray and black all over the seal. Leave the middle white, and the make the sides darker. How darker you make it how deeper the relief will be. This part is very experimental and you may have to come
back later and try it again. Here is what I did:

Most letter seals have a logo or a weapon on them. So find yourself a nice logo/weapon or use a letter. I used an eagle as a logo, you can use whatever you want. Position it in the center of the seal and fill with white.

Now go to Filters>Render >Lighting Effects and choose the settings you like, but be careful to select the texture channel "Alpha". I used: Light type Directional, Intensity 47, Gloss -18, Material -100, Exposure 0, Ambience 2 and Height 100. These setting are pretty experimental,
you can probably get a better look if you mess around a bit.

Now you're done. But it will look more nice if you put it on the map we did some tutorials ago. Here it is: