1) Make a new, blank, 400x100, transparent background project. RGB color and etc.

2) Press [Ctrl+D] on your keyboard to reset the colors to default, then click your Gradient Tool.

3) Make five or six clicks with the Gradient tool, but make sure that the settings are on 'Difference.' It should look something similar to this by now:

4) Press [Ctrl+U] on your keyboard, or go to Image>>Adjustments>>Hue/Saturation. A window should pop up. Click on [Colorize], then adjust the color to whatever you want. This is my example:

5) Now, go up to Layers>>New>>Layer...

6) In this new layer, go to Filter>>Render>>Clouds. Press [Ctrl+F] as many times as you need if you didn't get a cloud selection you like.

7)Color your clouds with [Ctrl+U]; try to use colors similar to the layer beneath it, if not the same colors.

8) Now go to your [Layers] window and move this colored cloud layer beneath the gradient. After doing this, change the layer blending of the gradient to [Hard Light]. It doesn't truly matter what you want to use; I prefer Hard Light because it gives a better effect.

You now have a nice little abstract background you can use for your signatures.

Optional Steps: 1) Make a new, transparent layer over the merged ones and select your Brush tool. Choose a nice brush that you feel will suit the purpose, then stamp it once in the color white.

2) After this, go to the Layers window again and move the stamped layer to the bottom, under the clouds layer. Make the blending for the cloudy layer into Hard Light as well.

3) Using the lasso tool [Be sure that your Feather is on 20px], select the stamped layer and make a figure like this:

Then press [Ctrl+I] to invert the selection like this:

Afterwards, delete the selected parts. It should look like this:

To make it blend better, change its opacity to 42%. [Anything works, really, as long as you can see it]

5) Make a new layer above all previous layers. Take the pencil tool, and with a 1px brush, black, make horizontal lines across the image. Space them with 1 px in between.

Then, go to Opacity and make it 13%. [Be sure you can still see it, but not so much that it overtakes your background.]

6) For text, fill in a bit of text wherever you want; in this case, since the left side seems so empty, I'll put my text there.

7) Do whatever you want to your text; make it glow, shadows, etc.

8) [This is a completely optional step that is rather useless if you think about it.] Take up your lasso tool once more and make an outline around your text. Afterwards, select the layer with the lines and press delete twice. This will make the background for your text clearer and outline it a bit. With that all said and done; you are finally finished! Apply different colors, brushes, patterns, etc. and see what you can come up with. My final product: