With the image directory you can change it to whatever location you want by simply going to 'Additional CSS Definitions' and change the following:
PHP Code:
background: url(images/misc/ext_term.gif) no-repeat 0;
To this for example.
PHP Code:
background: url(newstyle/images/misc/ext_term.gif) no-repeat 0;
This code is repeated three times. As for the error you are getting is a bug in the script and certain version of php/servers. I've created new code to try for the next release which I hope will fix this issue.