Here is a quick an easy way of making a brushed steel texture.
I'm using photoshop but it works just as well in GIMP (I've tried it)
Many experienced photoshoppers probably know this technique but for those that don't here we go:
Create a new document any size, say 800x600. Now choose a nice steel coloured grey. (TIP you can actually use any colour and get good effects, it just won't look metallic if you use a colour such as blue, alternatively use a gradient for a bit more of a realistic effect)
Now use bucket fill to colour your image grey.
Now we need to add some noise Filter>Noise>Add Noise (in GIMP I use HSV noise filter), make sure you check the box 'Monochromatic' and choose an amount somewhere from 10 to 30 depending how close you want the grain in the final image (I've used 25.98%).:
Next step is to add motion blur, this will give you the grain. Filter>Blur>Motion Blur. For a realistic effect use a distance between 30 and 50 pixels, I used 40 (TIP DO experiment with this value, try taking it up to 800pixels for some cool looking wallpaper lines, especially if you've used a colour other than grey)
Also here you will need to choose which direction you want the grain to run, I've chosen 90 degrees.
Almost done, but if you look at the edges you will see that 2 of the edges don't quite match the rest of the image and look messy, you have 2 options here, either crop your image or the method I prefer: take your rectanglular marquee tool and select a box around the parts you want to keep, next hit Control + T and scale your selection to match the canvas size.
You are pretty much finished here, but to make it look a little more realistic (and if you used a solid colour not a gradient) go Filter>Render>Lighting Effects... and play around with the settings to get realistic shading.
Finally give it some sharpening with the unsharp mask (Filter>Sharpen>Unsharp Mask) and if you desire adjust the curves or levels.
My Final Result:
I hope some people have found this useful.