Edit the "Note" variable to change the text displayed in the note block. For example, instead of the toolkit rendering "Note:" prior to the note text, you could have it say, "Don't forget:".
To customize note images:
1. Go to line 239 of en.xml
2. Change the path to a new note image
OR
2. Copy a new image into mypdf\cfg\common\artwork and use the same name as specified in en.xml.