Use your Paint Shop Pro 8 or later.
Make a Brushmark or a Selection of a Picture on a transparent Background.
Go to Export and Export as png with transparent Background to the Map C:\Documents and Settings\Your Map\Documents\Paint.net User Files\Custom Brushes.
When you open your Paint.Net and chooses Effects and Draw with Custom Brush, your new Brush is ready for Use. You may reduce a Selection to app. 150 pixels.
This Procedure may work with other graphic Programs with transparent Background and Export.
Sorry for my English, but I am a Dane.
Kindly
Jens Fr. Hansen
jenle@mail.tele.dk