Created from a public domain photograph originally made by Master Sergeant Jose Lopez, Jr. of the United States Air Force:
http://commons.wikimedia.org/wiki/Image:Emperor_penguin_chicks_at_Sea_World_%C2%B7_DF-ST-90-04598.JPG
Created using Paint.NET (http://www.getpaint.net/) and Potrace (http://potrace.sourceforge.net/).
This image was donated by Pearson Scott Foresman, an educational publisher, to Wikimedia Commons, and is thereby in the Public Domain. --- See http://commons.wikimedia.org/wiki/Category:Pearson_Scott_Foresman_publisher
These are recent images I converted to vectors with this command:
for i in *.jpg; do convert "$i" "`basename "$i" .jpg`.png" && autotrace -despeckle-level 15 -color-count 6 -input-format PNG -output-file "`basename "$i" .jpg`".svg -output-format svg "`basename "$i" .jpg`.png"; done
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Try it!