Kongregate is a community-driven browser games portal with an open platform for all web games.
Get your games in front of thousands of users while monetizing through ads and virtual goods.
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in your profile (via the My Profile link at the top)
choose edit account near the top by your current avatar (picture)
there is a textbox and browse button about half way down, use that to upload the picture you would like :)
needs to be 40×40 pixels
Save the settings and voila