You can find the images in the themes-folder
/usr/shar/themes/YOURTHEME/images/

The files were:
wmTaskLauncherIcon.png
wmTaskLauncherIconPressed.png
wmTaskSwitcherIcon.png
wmTaskSwitcherIconHighlight.png
wmTaskSwitcherIconPressed.png

As far as I know there is no easy way to position the home-button to the bottom of the screen.