Themeza.com has a boatload of themes for Moodle 1.9 if you're looking for something a little beyond the default set. Each has a high quality header image which might be modified to fit your own color schemes or logos. Note...
Check out this cool "tropical" theme from Themza posted recently (and download it for free!): http://bit.ly/cM47ez. Loads of themes available in the Themza Moodle theme repository: http://blog.themza.com/moodle