This is a tutorial I made for my friend. It is a full signature tutorial with a slanted 3D effect.
Ok make a new document any size. Mine is 350x140. Fill the background with Black. Get some brushes and brush with white. Then make a new layer and brush with black. Repeat this process switching between Black and White.

Grab a render. Im using this one.

And place it into your sig. Resize it using CTRL + T. Once your happy with the size press CTRL + U and set the saturation level to -100.

Ok now we need to add color. Make a color balance layer by going to
Image > Adjustments > Color balance These are the settings I used but you can do different.
Midtones - 45, 26, -62
Shadow - -30, 19, -62
Highlights - 0, 0, 0
Now render clouds.
Filter > Render > Clouds and make another colorbalance layer.
Midtones - 47, -39, 47
Shadow - 0, 0, 0
Highlights - 39, -43, 34
And redner clouds again and make a final colorbalance layer.
Midtones - -29, -31, 20
Shadow - 0, 0, 0
Highlights - 0, 0, 0
And render clouds.

Ok now add a border. Make a new layer and press CTRL + A and then goto
Edit > Stroke > 3pxl > Black > okThen
Edit > Stroke > 2pxl > White > okThen
Edit > Stroke > 1xl > Black > okSet that layer to
Soft lightNow add some text. Once your happy we can make the signature slanted. Click the top layer and press CTRL + SHIFT + E to merge all layers. Press CTRL + A to select the whole image and then copy it.
Open a new document the same size but 20pxl wider and higher. Paste the signature into this document (transparent)
Go to
Edit > Transform > Distort Move the corners around untill you have a slanted look. Right click the layer and set these blending options.
Drop shadow - Distance 8, Spread 31, Size 0.
Now goto
File > Save as Make sure it is saved as a .PNG file.