Bullet Holes

Choose a texture or image you want to add the bullet hole to, you may take my texture to the left, if you'd like.

Choose a nice appropriate section for the bullet hole, create a new layer, then using the Elliptical Marquee Tool, hold down Shift and draw a circle, now select the Lasso Tool, with you circular selection still active, hold Alt (Mac: Option) and take a way some pixels from the edges to give the circle a rough look, fill the circle in with black.

Create a new layer. Using the Lasso Tool, make a selection of a shard of metal starting from the edges of the circle you made. I suggest you zoom in really close and make the metal shard jagged. Now that you've done that, with your selection still active, make the layer with your texture active and copy by hitting Ctrl+C (Command+C). Then, go back to the layer that you created for the metal shard and Paste by hitting Ctrl+V (Command+V). Now, select the Burn Tool, in the Options Bar, set its Range to Shadows and pressure to about 5%. Zoom in a little, and use the Burn Tool give the metal shard shading so it looks bent. Then, take the Sharpen Tool, set the pressure to about 45%, and sharpen some parts of the metal shard. Next, choose the Burn Tool, and add some more shade, going over your previous shading too.

Now, create a new layer underneath the one with the metal shard, load the selection of the metal shard by holding Ctrl (Command) and clicking the layer in the Layers Palette. Fill the selection with black, and go Filter>Blur>Gaussian Blur with a radius of 2 pixels. Repeat the process for as many metal shards as you would like to add. When you are finished you should have something like this.