For those that are not points/units driven or are... These are really a fun addition to self accomplishments
As I understand it... Each badge changes the background color as you achieve new levels in each project. For example...
Say you chose GO Fight Against Malaria. The main body of the badge never changes and looks like this

but the background does each time you return a certain amount of completed work. The background colors go like this...






And for those that are using SNURKS sig... The lower bars are all of the causes and they match the colors achieved in the badges (As I understand it, to be corrected if I am mistaken).
You can see your badges with every post you make on the WCG forums or you can look in your "My Grid" and it shows you a list (Once you have any).
I came across this thread, that linked me to a post.. That helps explain them a little for each cause as well...
See here
Badge for participation Active GO Fight Against Malaria
http://bit.ly/sXeKQC
Drug Search for Leishmaniasis
http://bit.ly/pBFFt6
Computing for Clean Water
http://bit.ly/9i5bz6
The Clean Energy Project Phase 2
http://bit.ly/9LtG3U
Help Cure Muscular Dystrophy Phase 2
http://bit.ly/brWAoo
Help Fight Childhood Cancer
http://bit.ly/phsDeH
Help Conquer Cancer
http://bit.ly/a48B1o
Human Proteome Folding Phase 2
http://bit.ly/qcrAX7
FightAIDS@Home
http://bit.ly/bUkQbX
Intermittent Discovering Dengue Drugs Together Phase 2
http://bit.ly/p3IY1W
Beta Testing
http://bit.ly/qx5r6G
Inactive Influenza Antiviral Drug Search
http://bit.ly/dvnCUb
The Clean Energy Project
http://bit.ly/qcafVK
Discovering Dengue Drugs Together
http://bit.ly/bvjUe4
Completed Nutritious Rice for the World
http://bit.ly/9z3MIv
AfricanClimate@Home
http://bit.ly/oGkneN
Help Cure Muscular Dystrophy
http://bit.ly/dB8Zz9
Genome Comparison
http://bit.ly/qI5Z8Z
Help Defeat Cancer
http://bit.ly/b7531e
Human Proteome Folding
http://bit.ly/nwS6ot
Grey Background Active GO Fight Against Malaria
http://bit.ly/ttFRU9
Drug Search for Leishmaniasis
http://bit.ly/ppPAn5
Computing for Clean Water
http://bit.ly/oDNkim
The Clean Energy Project Phase 2
http://bit.ly/qO0PHl
Help Cure Muscular Dystrophy Phase 2
http://bit.ly/nVxU0Z
Help Fight Childhood Cancer
http://bit.ly/9HSaLH
Help Conquer Cancer
http://bit.ly/nWM564
Human Proteome Folding Phase 2
http://bit.ly/auMg5I
FightAIDS@Home
http://bit.ly/r7B8C6
Intermittent Discovering Dengue Drugs Together Phase 2
http://bit.ly/aUrN2I
Beta Testing
http://bit.ly/aKn7uQ
Inactive Influenza Antiviral Drug Search
http://bit.ly/nn2W4V
The Clean Energy Project
http://bit.ly/bMfa3B
Discovering Dengue Drugs Together
http://bit.ly/njh4ta
Completed Nutritious Rice for the World
http://bit.ly/oSG98R
AfricanClimate@Home
http://bit.ly/bJYXMJ
Help Cure Muscular Dystrophy
http://bit.ly/oyTC1T
Genome Comparison
http://bit.ly/cfHwb0
Help Defeat Cancer
http://bit.ly/oMdFjE
Human Proteome Folding
http://bit.ly/ao9j5b