On /usr/share/themes/blanco/meegotouch/constants.iniand/usr/share/themes/blanco/meegotouch/proto/constants.ini, you will see a few references to PNG files prefixed with "dev_". Remove the "dev_" part from the filenames.
On /usr/share/themes/base/meegotouch/sysuid/style/statusarea.css , you will see two references to PNG files prefixed with "dadd-". This time, there's no unbranded version of those bitmaps, but the solid color background is fine either way. So, just entirely remove both lines.