Splinter Cell: Double Agent - How to get more skins for your character

Achievements:
Complete each of the following achievements below to get the allotted gamerscore.The Invisible Man 20 In solo mode, complete a mission without being detected.
Getting Technical 20 In solo mode, knock out 5 enemies using non-lethal gadgets.
Hero 20 In solo mode, complete the game with the best ending.
Teacher's Pet 40 In solo mode, successfully complete all of the training courses.
Training Completed 10 In solo mode, successfully complete a training course.
The Collector 20 In solo mode, collect all gadgets and upgrades.
The Human Light Switch 20 In solo mode, use your EMP Pistol to turn off 20 light sources.
Professional Ninja 40 Complete solo mode on Hard difficulty.
Agent of the Month 20 Complete the profiles of all the major members of the JBA.
RECRUIT 10 Obtain an overall characteristics average of over 1.
OPERATIVE 15 Obtain an overall characteristics average of over 5.
FIELD AGENT 20 Obtain an overall characteristics average of over 20.
SPECIAL AGENT 25 Obtain an overall characteristics average of over 45.
OFFICER 30 Obtain an overall characteristics average of over 75.
COMMANDER 45 Obtain an overall characteristics average of over 95.
Bronze Trophy 15 Complete all the challenges by obtaining at least the bronze medal.
Silver Trophy 30 Complete all the challenges by obtaining at least the silver medal.
Gold Trophy 50 Complete all the challenges by obtaining at least the gold medal.
BLACKWING Expert 20 Get at least 10 victories as a spy and 10 in the UPSILON FORCE and play 25 sessions in this map.
MOTORWAY 90 Expert 20 Get at least 10 victories as a spy and 10 in the UPSILON FORCE and play 25 sessions in this map.
TERMINUS Expert 20 Get at least 10 victories as a spy and 10 in the UPSILON FORCE and play 25 sessions in this map.
SLAUGHTER HOUSE Expert 20 Get at least 10 victories as a spy and 10 in the UPSILON FORCE and play 25 sessions in this map.
RED DIAMOND Expert 20 Get at least 10 victories as a spy and 10 in the UPSILON FORCE and play 25 sessions in this map.
BOSS HOUSE Expert 20 Get at least 10 victories as a spy and 10 in the UPSILON FORCE and play 25 sessions in this map.
DAWN WAVES Expert 20 Get at least 10 victories as a spy and 10 in the UPSILON FORCE and play 25 sessions in this map.
USS WISDOM Expert 20 Get at least 10 victories as a spy and 10 in the UPSILON FORCE and play 25 sessions in this map.
Ellsworth Assignment Completed 30 In solo mode, completed the Ellsworth Penitentiary assignment.
Iceland Assignment Completed 30 In solo mode, completed the Iceland assignment.
Save Hisham In solo mode, saved Hisham's life