This is a simple wallpaper that I made using Adobe Photoshop CS3.I`m not really good at it but I can give some explaination about the basic.
Firstly open the picture file that you want to use as your background.
Then,open another file.Use Rectangular Marquee Tools(On the left side of the screen) and mark the whole picture.After that,copy it (Ctrl+C).
And then paste it (Ctrl+V) on the previous picture.Click on edit,and choose Free Transform to make it easier to move,resize and rotate the picture.
Do the same thing on the other picture file.
Stack all the picture together and arrange it nicely.Now you`re nearly done! Next select the Type Tools.Type it anyway you like,use Set the Font Family if you want to change the font.You can even change the colour if you want to.Just click Swatches and choose any colour you want.If you think that isnt enough you can even make it stylish(click on styles) and also you can adjust the RGB(click on color).Oh,almost forgot.If you want to adjust the transparency of the picture,just click on layer and control the Opacity or Fill.
There you have it.A simple and a basic way to use Photoshop.