Open photo in IrfanView, go to ‘Edit’ menu and select ‘Create Custom Crop section…’ or press Shift+C (shortcut key).
Then select ‘none’ in the ‘Set ratio for width: height:’ column and select ‘pixel’ then enter ‘Width:’ 480 and ‘Height:’ 800 in the ‘Selection size/position:’ column.
Then right click your mouse and hold. Now you can move your mouse (the crop border will move) to the best spot in your photo to be your WVGA wallpaper. If accidentally you lose your crop border repeat step 1 above.
If you find your crop border is too small. Go to edit and select ‘Maximize and center selection’.
After you find your desire image for WVGA wallpaper, select ‘Crop Selection’ or press Shift+Y (shortcut key).
Then go to ‘Image’ and select ‘Resize/Resample…’ or press Ctrl+R (shortcut key). Then enter ‘Width:’ and ‘Height:’ and select ‘unit’ as ‘pixels’. You actually need to enter only 1 value either width or height and the other value will automatically feed to your current photo aspect ratio. After finish click OK.
Congratulation! You have created your own WVGA wallpaper.