Tips about how I made the Autumn leaves wallpaper (see wallpaper).
This wallpaper has been made with custom-created brush. To start, we need a leaf. Here is a leaf I found in Interned. You can also bring a leaf from the street and scan it :-)
Crop leaf image as necessary, desaturate (Ctrl-Shift-U).
Invert (Ctrl-I) and adjust layers (Ctrl-L) to increase contrast.
Use Magic Wand (W) to remove white background.
Go to Edit menu - Define Brush preset.
Now, when brush is ready, create new document (it will be our wallpaper). Fill it with solid color.