Otherwise windows takes a BMP of the screen when you hit printscreen.
Kind of strange.
Nevertheless, use a .png for your additions. 
2.4. Custom character portraits
-You can insert your own portrait into the game for use as a custom character.
Create a 211x256 pixel .PNG file with your character portrait and
save the file to the C:\Program Files\Ubisoft\Stardock\PolMachine\Gfx\Candidate
directory.
For example, saving the file with Adobe Photoshop, you should save
a 24-bit .PNG with transparency to the above directory.
Welcome Guest! Please take the time to register with us.
- Richer content, access to many features that are disabled for guests like commenting and posting on the forums.
- Access to a great community, with a massive database of many, many areas of interest.
- Access to contests & subscription offers like exclusive emails.
- It's simple, and FREE!