[strra]

what i've done in the past is to take the .tsk theme file and unzip it (with winrar) to a folder on your pc then find out what files are the two (landscape and portait) wallpapers. then take your two wallpapers, change them to the name of the ones in the tsk and overwrite the original two.
then use a program called "makev3" to make a cab file with all the files in it... then just rename it from .cab to .tsk then put it back in your windows folder.... now you have a theme with your custom wallpapers