Sure.

All I did was open the male_heads.png file I found in the Virtual Villagers The Lost Children/Images folder with Paint... but...

First and most important!!
Rename the original file you find in the Images folder with a .bak extension, so you can go back to the original if you mess something up.

Okay, after you've protected the original file, copy it to your desktop and give it it a .png extension again. Then you can change the heads the way you want them to look, using either Paint or another graphics program, and save the file to your desktop again. After that, if you've used Paint, open the file with Adobe (or any other program capable of making the background transparent), make the background transparent again, and save it to your desktop in non-interlaced format. I would suggest stashing a copy of it in the LDW folder in My Documents.

After that, copy it from your desktop into the VV2 Images folder under the original filename: male_heads.png

That's about it.

(By the way, the only reason I used Paint was that I just got Adobe and am not familiar with it yet.)