Step 1: Lay Down a Little Grunge
Start with a small image, I use 400x170. Then dump the background black, create a new layer and brush a little bit of grunge on. I use a brush set from 22pixels flock called Sneaky_GFX_Dragoneye. I only used two brushes. Drop the opacity of that layer down to 40% or so.
Step 2: Some Soft Abstract
Create a new layer and brush a little bit more with a set of abstract brushes. I used Jashin's brushes set 10, which is downloadable from deviantart.com. Drop the opacity down to 50% or so.
Step 3: Bash It Up
There is a set of brushes called Bash's set 12, downloadable from deviantart.com. They are very unique brushes, and can cause an incredible effect if used in the right place. I find that bash's brushes look best around the edges, but feel free to experiment. Create a new layer and brush some on. Set the blending mode of that layer to "Soft Light"
Step 4: Add Some Stuff to the Emptiness
Sometimes, when you do this there is some leftover black space. That is not good. You need to fill that stuff up. I used jashin's dirty abstract brushes for that. Downloadable from deviantart.com. Drop the opacity of this layer down to 50% or so.
Step 5: Fractalize It
Using some fractal brushes (I used orsonsfractals, from deviantart.com) brush some more. Drop the opacity of this layer down to 70% or so.
Step 6: Fractalize It-AGAIN!
Using some more fractal brushes, brush some more. Don't drop the opacity on this layer.
Step 7: Darken
Merge the layer into one layer by pressing cntrl+shift+e. Then go to enhance>adjust brightness and contrast>brightness and contrast. Set the brightness to -40 and the contrast to +40.
Step 8: Techit
Using some tech brushes create a little platform. Then duplicate the layer. Go to edit>stroke>1px black brush on that layer. Drop the opacity of the non stroked layer to 50% or so. Then set the stroked layer to "darken."
Step 9: Color!
Create a new layer underneath the tech layers. Using a 65 px soft brush start to add the colors that you want. After you have that, go to filter>noise>median and set the amount to 45 pixels or so. Then go to filter>blur>gaussian blur and set the amount to 50 pixels or so. Now, got to enhance>adjust color>hue and saturation and drag the saturation slider down to -65 or so. Then set the layer to "color."
Step 10: Render it Awesome
Put your render in, resize it, and place it in a location you like. Drag it underneath the color layer. Then, take the lassoo tool and set the feather to 40 pixels. Now select part of the render. Cut it, and paste it onto a new layer. Use the nudge tool to put it right on top of where it was before you cut it. THat way it will be part of the normal color, and part of the background color.
Step 11: Text!
Add some text on top of that platform that you made with the tech brushes. Bam! You're done!
Notes
*Remember the thirds rule. Divide the banner into imaginary thirds. The render should go on the dividing line between the middle and one of the outer thirds usually. There are exceptions, like the image in my sig. The render would interfere with the text, so I had to stick it lower and farther to the right.
*Bright colors are not good. Try to stay with very low saturation colors, or else it'll look crappeh, k?
*Borders. Yes, I didn't mention borders, but they're usually a good idea. Stick with a 1 pixel black brush, k. It'll probably look the best. If you want to look fancy, then you'll want to do a 2 pixel colored brush, then a 1 pixel black brush on top of it (see sig for an example.)
*Text. There are a number of styles you can do text. My favorite is a black outline, on top of a layer with colored text, then set the colored layer to linear light. Nice effect. (See the tut text for an example.)
*Fonts. People all have their preferred styles for fonts, but commonly used are pixel fonts. A few recommendations are Silkscreen, pixeldust, sevenet7, Visitor TT2 (BRK), and aerial.
*Gradients. Another way to color things is through gradients. On a new layer, you can use two gradients, in my sig I used yellow and blue, and put them in a style that looked good on this banner.
*Coloring from the start. If you don't plan on brushing a lot and having some black space, which is cool, then you might want to brush in color from the start. It's very hard, IMO to get a good effect, but sometimes it looks better then my coloring method.
Here's a banner I made with coloring from the start
*Tech stuff is totally optional. I just think it looks c00l.
BRUSHES
a huge brush set is here
http://22pixels.com/flock.php
download it. it also has tons of fonts. yes, it CS only, but download it on any other version and some of the brush sets will work. not all of them, unfortunately, but some of them.
also, here are some links to good brush sets
http://j-a-s-h-i-n.deviantart.com/
http://b-a-s-h.deviantart.com/
http://o-r-s-o-n.deviantart.com/
http://files.filefront.com/Brusheszip/;4111406;;/fileinfo.html
Tech brushes
http://genuine-atramentous.deviantart.com/ - get the Tech Set .1659.
http://www.greycobra.com/downloads/view/13/ - download 'em